A compact microwave tunnel furnace

Abstract

The present invention provides a compact microwave tunnel furnace comprising a microwave suppressor A, a microwave cavity, and a microwave suppressor B, which are sequentially connected. The furnace also includes at least one microwave source. Each microwave source inputs microwave energy into the microwave cavity through a corresponding microwave feed port. The upper port of the microwave feed port is flush with the inner bottom surface. The minimum distance H between any point on the inner bottom surface and any point on the inner top surface of the microwave cavity is less than or equal to the minimum operating wavelength λ of all microwave sources. By compressing the height of the microwave cavity, the present invention arranges all microwave sources on the bottom surface of the microwave cavity and positions a conveyor belt close to the bottom surface of the microwave cavity. This improves the determinism of the heating electromagnetic field and the heating efficiency of the equipment, while also facilitating easy cleaning of the interior of the equipment. The present invention has a simple structure and can be used for large-scale heating and drying of various materials.

Description

Technical Field

[0001] The present invention relates to the field of uniform and efficient microwave heating or drying, and in particular to a compact microwave tunnel furnace. Background Art

[0002] Microwave heating can replace various traditional heating methods. Microwave equipment uses microwave energy to heat a variety of materials, including but not limited to wood, grain, medicinal herbs, spices, and dairy products. In the field of microwave chemistry, microwave energy is used to accelerate various chemical reactions. Microwave energy is also used in the production of various new materials, such as nanomaterials and synthetic diamonds.

[0003] A tunnel oven is a type of heating device that can continuously heat or dry materials and has been widely used in industry. Microwave tunnel ovens utilize bulk heating, replacing traditional conductive heating methods such as electric or gas heating. This can increase heating speeds by several to dozens of times, offering promising applications. A microwave tunnel oven generally consists of a microwave suppressor, a microwave cavity, another microwave suppressor, an output port, multiple microwave sources, at least one conveyor belt, and an object to be heated that is positioned above and moves with the conveyor belt. Each microwave source inputs microwave energy into the microwave cavity through a microwave feed port. The conveyor belt contacts the inner bottom surface of the microwave cavity. The microwave suppressor prevents microwaves in the microwave cavity from leaking out of the tunnel oven's output port. The object to be heated is positioned on the conveyor belt and moves along with it, receiving microwaves from the microwave cavity. The microwaves interact with the object in the microwave cavity, heating it, and then exiting through the output port. The microwave cavity, also commonly referred to as a heating chamber, provides a space for interaction between the object to be heated and the microwaves.

[0004] However, compared with its theoretical advantages, the international application of microwave tunnel furnaces is still in its infancy. Two key technical problems seriously limit the application of microwave energy: heating unevenness and low heating efficiency.

[0005] In traditional microwave tunnel furnaces, the microwave cavity is mostly rectangular, with three-dimensional dimensions far exceeding the operating wavelength of the microwaves generated by the microwave source. The large length and width of the microwave cavity are necessary to increase production capacity. The high height of the microwave cavity is one reason for this, in part to facilitate cavity cleaning. Within any cavity, such as a microwave cavity, electromagnetic waves resonate in the form of various natural modes of the cavity. At a certain operating frequency, multiple modes are excited simultaneously, with the electric field amplitude at some locations in space reaching its maximum and at others reaching its minimum. At the typical microwave energy application frequency of 2450 MHz, the distance between these electric field concentrations is half the operating wavelength of the microwave used, approximately 62 mm, resulting in unevenness in the heated object along this scale.

[0006] To address the issue of microwave heating uniformity, researchers both domestically and internationally have made tireless efforts. However, due to the immense complexity of the problem, the microwave community lacks clear theoretical guidance. Three-dimensional electromagnetic simulations are also computationally intensive and difficult to perform. Consequently, researchers worldwide are pursuing an uncertain path in their search for answers. To this end, researchers have increased the number of microwave sources to dozens or even hundreds, employed microwave feed ports of varying shapes, placed microwave sources on the top, bottom, or even the left and right sides of the microwave cavity, altered the polarization direction of the electric field at the rectangular waveguide microwave feed ports, employed microwave sources of varying frequencies, and employed sources with the widest possible spectrum. These attempts to improve heating uniformity by increasing the complexity of the schemes have been successful. These approaches rely heavily on empirical experience and encounter the technical challenge of accurately measuring the electromagnetic field in large microwave cavities. Consequently, the issue of heating uniformity in microwave ovens, particularly large microwave tunnel ovens, remains unresolved. Summary of the Invention

[0007] The purpose of the present invention is to provide an innovative solution to solve the problems of heating unevenness and low heating efficiency in traditional microwave tunnel furnaces.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a compact microwave tunnel furnace, comprising a microwave suppressor A, a microwave cavity, and a microwave suppressor B, which are connected in sequence; and at least one conveyor belt for carrying a heated object and driving the heated object to move with the conveyor belt, the conveyor belt passing through the microwave suppressor A, the microwave cavity, and the microwave suppressor B in sequence. The inner surface of at least one section of the microwave cavity includes an inner top surface, an inner bottom surface, an inner side surface A, and an inner side surface B; the inner top surface and the inner bottom surface are arranged opposite each other, and the inner side surface A and the inner side surface B are arranged opposite each other; the furnace also comprises at least one microwave source, each of the microwave sources inputs microwave energy into the microwave cavity through a corresponding microwave feed port, the microwave feed port being arranged on the inner bottom surface, and the upper end of the microwave feed port being arranged flush with the inner bottom surface, the inner top surface being part of a plane without any microwave feed port; the minimum value of the distance H between any point on the inner bottom surface and any point on the inner top surface of the microwave cavity is less than or equal to the minimum value of the operating wavelength λ of all microwave sources; the conveyor belt includes a carrying section for carrying the heated object, the carrying section being in contact with the inner bottom surface of the microwave cavity.

[0009] Preferably, the minimum value of the distance H between any point on the inner bottom surface and any point on the inner top surface of the microwave cavity is less than or equal to half of the minimum value of the operating wavelength λ of all microwave sources.

[0010] Preferably, the minimum value of the distance H between any point on the inner bottom surface and any point on the inner top surface of the microwave cavity is less than one quarter of the minimum value of the operating wavelength λ of all microwave sources.

[0011] Preferably, at least two microwave feed ports are arranged on the inner bottom surface; and no microwave feed port is arranged on the inner top surface.

[0012] Preferably, all microwave feed ports are arranged on the inner bottom surface.

[0013] Preferably, the inner bottom surface is a part of a horizontal plane or the normal direction of any point on the inner bottom surface is opposite to the direction of gravity, or the angle between the two is greater than 90 degrees and less than 180 degrees.

[0014] Preferably, at least two of the microwave feeds are rectangular waveguides, wherein the operating mode is TE 10 model.

[0015] Preferably, all the microwave feeds are rectangular waveguides, and the working mode is TE 10 model.

[0016] Preferably, the direction of the electric field in the microwave feed port is consistent with the moving direction of the conveyor belt.

[0017] Preferably, the direction of the electric field in the microwave feed port is perpendicular to the moving direction of the conveyor belt.

[0018] You can be specific:

[0019] The inner bottom surface may be the entire bottom surface of the microwave cavity, or may be a part of the entire bottom surface of the microwave cavity.

[0020] The microwave cavity here is generally a tubular space with an axis extending from the microwave suppressor A to the microwave suppressor B. The section of the microwave cavity here refers to a portion of a single-connected continuous space cut out from the tubular space.

[0021] When a portion of the object being heated moves along the conveyor belt within the microwave cavity and reaches a microwave feed port, we position the object as close to the microwave feed port as possible to ensure that the microwave field experienced by the object is as uniform as possible and minimizes the impact of the microwave cavity structure and microwaves from other feed ports, thereby significantly improving microwave heating uniformity. To this end, we position the object on the conveyor belt and ensure that the belt is in contact with the inner bottom surface of the microwave cavity.

[0022] Generally, the inner bottom surface is located in a horizontal upward plane, that is, the inner bottom surface is part of the horizontal plane. However, we do not rule out the possibility that the inner bottom surface is tilted for some purpose: the normal direction of any point on the inner bottom surface is opposite to the direction of gravity, or the angle between the normal direction and the direction of gravity is greater than 90 degrees and less than 180 degrees.

[0023] To minimize the volume of the microwave cavity, which can reduce the number of modes in the cavity that can be simultaneously excited by a microwave source within a certain frequency range, achieving a "deterministic" design, and to improve the isolation between different microwave feeds and enable the use of a distributor to improve the matching degree and matching bandwidth between any microwave feed and its connected microwave source, we impose a height restriction on the microwave cavity: the minimum distance H (height) from any point on the inner bottom surface to any point on the inner top surface of the microwave cavity must be less than the minimum operating wavelength λ of all microwave sources. Note that multiple microwave sources can exist, each with a different operating wavelength. Therefore, the present invention utilizes height reduction to reduce the volume of the microwave cavity, thereby achieving a "deterministic" design.

[0024] Reducing the height of the microwave cavity can improve the performance of the device: the minimum distance H between any point on the inner bottom surface and any point on the inner top surface of the microwave cavity is less than half of the minimum working wavelength λ of all microwave sources.

[0025] Further reducing the height of the microwave cavity can further improve the performance of the device: the minimum distance H between any point on the inner bottom surface and any point on the inner top surface of the microwave cavity is less than one-quarter of the minimum working wavelength λ of all microwave sources.

[0026] In a preferred design, the minimum distance H between any point on the inner bottom surface and any point on the inner top surface of the microwave cavity is equal to one-quarter of the minimum operating wavelength λ of all microwave sources. If the microwave cavity height is smaller, while the amplitude of the electromagnetic field at a microwave feed port experienced by a heated object can be well determined, the heated object may come into contact with the inner top of the microwave cavity, hindering the transmission of the heated object. Furthermore, since the microwaves emitted by the microwave feed port are transverse waves with an electric field perpendicular to the propagation direction, the microwaves are almost totally reflected upon reaching the inner top of the microwave cavity. If the microwave cavity height is too small, it is difficult to establish a strong electromagnetic field within the microwave cavity. The microwave electromagnetic field will primarily reside in the transmission line outside the microwave feed port. This situation is not conducive to broadband matching between the microwave source and the microwave cavity. For magnetrons with a wide frequency spectrum, it will be difficult to deliver microwave energy into the microwave cavity, resulting in low microwave heating efficiency. Third, the electromagnetic field in the microwave cavity varies significantly along the normal direction of the microwave feed port, resulting in uneven heating of the heated object across its thickness. Since the conveyor belt and the heated object have a certain thickness, their relative dielectric constants are both greater than 1. Taking all factors into consideration, the height of the microwave cavity is slightly less than 1 / 4 of the working wavelength of the microwave source.

[0027] The inner surface of a microwave tunnel furnace needs to be cleaned after a period of operation, otherwise the burnt parts of the heated objects will affect the quality of the heated objects. The height of the microwave cavity of a traditional microwave tunnel furnace is generally chosen to be much larger than the operating wavelength of the microwave source, one of the reasons for this is to facilitate cleaning.

[0028] To effectively heat or dry the object with microwaves, we place as many microwave sources as possible on the inner bottom surface of the microwave cavity. At least two microwave feed ports are located on the inner bottom surface. No microwave feed ports are located on the inner top surface. In a preferred design, all microwave feed ports are located on the inner bottom surface.

[0029] Traditional microwave tunnel furnaces typically place microwave feeds on the inner ceiling of the microwave cavity, partly to facilitate the placement of the conveyor belt. However, this design presents the following challenges: 1) For any microwave feed shape, including coaxial, circular, and rectangular waveguides, the microwave field distribution near the feed is the most deterministic. In microwave cavities, especially those with very large overmold cavities, since both the object being heated and the conveyor belt are located on the inner bottom surface of the microwave cavity, a considerable distance from the feed, the distribution of the microwave field felt by the object becomes uncertain, influenced by the cavity shape and the influence of microwaves from multiple microwave sources. 2) Since the microwave feeds are located on the inner ceiling of the microwave cavity, it is difficult for the object being heated to reach the vicinity of each microwave feed. This requires the object to be approximately the same height as the microwave cavity, which could result in the object contacting the inner ceiling of the microwave cavity, thus hindering its transport. 3) If the conveyor belt is placed directly in close proximity to the inner bottom surface of the microwave cavity, interaction between the microwaves and the object being heated becomes difficult. Because the microwave feed port is located on the inner top surface of the microwave cavity, the transverse wave characteristics of microwaves make it difficult to establish a strong electromagnetic field near the metal inner bottom surface of the microwave cavity. 4) If the conveyor belt is directly adjacent to the inner bottom surface of the microwave cavity, the heated objects on the conveyor belt will be heated unevenly at different heights. This is due to the distribution of the electric field of the pure standing microwave wave caused by the total reflection of the downward-propagating transverse microwaves at the inner bottom surface of the microwave cavity.

[0030] For ease of cleaning and effective heating, traditional microwave tunnel furnaces sometimes suspend the conveyor belt in the microwave cavity. In this case, the height of the microwave cavity is much greater than the operating wavelength, making the microwave cavity much larger than the operating wavelength in all three directions. This exacerbates the uncertainty and complexity of the problem, making it difficult to successfully design a uniform and efficient microwave tunnel furnace.

[0031] In general, we use high-power microwave sources, especially magnetrons. Taking into account the requirements of power capacity and low insertion loss, the microwave feed is designed as a rectangular waveguide: at least two of the microwave feeds are rectangular waveguides. In a better design, all of the microwave feeds are rectangular waveguides. In order to reduce costs, the microwave feed generally selects a standard waveguide that includes the operating frequency of the microwave source. For example, when using an ordinary magnetron of 2450MHz as a microwave source, we choose BJ26 or BJ22 standard rectangular waveguide as the size of the microwave feed. This is because, regardless of the structure and size of the microwave cavity, since the microwave feed is a rectangular waveguide, the working mode therein is its fundamental mode TE 10 The field distribution in this mode is deterministic and independent of the microwave cavity. This design minimizes the effect of the size and shape of the microwave cavity on the electromagnetic field near a microwave feed port. When a portion of the heated object, moving along the conveyor belt within the microwave cavity, reaches a microwave feed port, its proximity to the microwave feed port significantly improves the determinism of the microwave electromagnetic field distribution and heating uniformity.

[0032] If a rectangular waveguide is used as the microwave feed port, there are two ways to set the orientation of the wide side of the microwave feed port, depending on the characteristics of the electric field distribution at the microwave feed port: the wide side of the microwave feed port is perpendicular to the direction of movement of the conveyor belt, and the direction of the electric field in the microwave feed port is consistent with the direction of movement of the conveyor belt; or the wide side of the microwave feed port is parallel to the direction of movement of the conveyor belt, and the direction of the electric field in the microwave feed port is perpendicular to the direction of movement of the conveyor belt. The first method allows us to use a metal wire conveyor belt for high-temperature heating or sintering. The second method often uses materials with weak microwave absorption, such as polytetrafluoroethylene, to make the conveyor belt. In this case, it is easier to achieve uniform microwave heating.

[0033] It should be noted that the present invention arranges all microwave feeds on the inner bottom surface of the microwave cavity, which is equivalent to setting up several heat sources with clear boundaries in the microwave cavity. Due to the spatial requirements for the installation of microwave sources and the need to isolate them from each other, these heat sources must be arranged in a row at a certain distance in the horizontal direction perpendicular to the direction of movement of the conveyor belt. However, due to the gaps between the microwave feeds, the heated objects passing through the microwave feeds in this row of microwave sources are not heated uniformly in the horizontal direction. To solve this problem, we can reasonably arrange several rows of similar microwave sources at a certain interval along the direction of movement of the conveyor belt. The microwave sources in each row are staggered at an appropriate distance in the horizontal direction, so that these microwave sources form an array of microwave sources. When the heated objects are transported on the conveyor belt, the heat sources provided by the array of microwave sources successively heat the horizontal parts of the heated objects, achieving the purpose of uniform heating.

[0034] The present invention provides a compact microwave tunnel furnace. The innovations of this invention include: 1) compressing the microwave cavity height to less than or equal to the operating wavelength of the microwave source; 2) arranging all microwave sources on the bottom surface of the microwave cavity; 3) placing the conveyor belt close to the bottom surface of the microwave cavity; and 4) placing the heated object as close as possible to the microwave feed port. The benefits of this invention include: 1) the microwave field near the microwave feed port is primarily influenced by the microwave source and microwave feed port, and is less affected by the shape and size of the microwave cavity, resulting in greater certainty. 2) due to losses in the heated object, the mutual coupling between different microwave feed ports is greatly reduced, allowing the use of a mixer to significantly improve the matching between each microwave source and the microwave cavity, thereby significantly improving the heating efficiency of the device. 3) The height of the microwave cavity is minimized, minimizing the effective volume of the resonant cavity that interacts effectively with each microwave source. Furthermore, the heated object is filled in the resonant cavity at the highest possible ratio, allowing each microwave source to be matched to the microwave cavity over the widest frequency band through the mixer, facilitating the use of microwave sources with large frequency drift and a wide frequency spectrum, such as magnetrons. This can further improve the heating efficiency of the device. 4) In the present invention, all feed sources are located on the bottom surface of the microwave cavity, while no microwave source is located on the top surface of the microwave cavity, making the top surface of the microwave cavity easily openable or uncovered. In this case, the top and bottom surfaces of the microwave cavity can be connected using hinges, hinges, or snaps, rather than screws. Compared to conventional microwave tunnel furnaces, where the top and bottom surfaces of the microwave cavity are typically connected using screws or welding, this device is significantly easier to clean.

[0035] To further increase the isolation between different feed ports, various structures can be added to the microwave cavity, such as periodically loading various metal pillars. Proper design of the height of the metal pillars and the spacing between adjacent metal pillars can significantly improve the isolation between different feed ports. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a side view schematic diagram of the present invention, Example 1 and Example 2.

[0037] Figure 2 for Figure 1 Schematic diagram of AA direction.

[0038] Figure 3 for Figure 1 Schematic diagram of BB direction.

[0039] Figure 4 For Example 2 Figure 1 Schematic diagram of BB direction.

[0040] Figure 5 This is a side schematic diagram of implementation example 3.

[0041] Figure 6 It is the existing technology.

[0042] Figure 7 It is a structural schematic diagram of the present invention.

[0043] The numbers in the accompanying drawings correspond to the following names: 1-microwave suppressor A, 2-microwave cavity, 3-microwave suppressor B, 4-microwave source, 5-conveyor belt, 6-heated object, 7-microwave feed port, 21-inner top surface, 22-inner bottom surface.

[0044] Some of the terms in this manual are defined as follows:

[0045] Working wavelength, the wavelength in air corresponding to the working frequency of a microwave source of the microwave tunnel furnace.

[0046] Microwave feed port: The interface between the transmission line through which a microwave source of the microwave tunnel furnace feeds microwave energy into the microwave cavity and the inner surface of the microwave cavity. DETAILED DESCRIPTION

[0047] Example 1

[0048] like Figures 1 to 3 shown.

[0049] A compact microwave tunnel furnace comprises a microwave suppressor A1, a microwave cavity 2, and a microwave suppressor B3, which are connected in sequence; a conveyor belt 5 for carrying a heated object and driving the heated object 6 to move with the conveyor belt 5; the conveyor belt 5 passes through the microwave suppressor A, the microwave cavity, and the microwave suppressor B in sequence; the inner surface of the microwave cavity 2 comprises an inner top surface 21, an inner bottom surface 22, an inner side surface A, and an inner side surface B; the inner top surface and the inner bottom surface are arranged oppositely, and the inner side surface A and the inner side surface B are arranged oppositely; and the furnace further comprises three microwave sources (magnetrons). Any one of the microwave sources inputs microwave energy into the microwave cavity through a corresponding microwave feed port, the microwave feed port is arranged on the inner bottom surface, and the upper port of the microwave feed port is arranged flush with the inner bottom surface, and the inner top surface is a part of the plane on which no microwave feed port is arranged; the minimum value of the distance H between any point on the inner bottom surface and any point on the inner top surface of the microwave cavity is less than or equal to the minimum value of the operating wavelength λ of all microwave sources; the conveyor belt includes a bearing section for carrying the heated object, and the bearing section is in contact with the inner bottom surface of the microwave cavity.

[0050] The minimum value of the distance between any point on the inner bottom surface and any point on the inner top surface of the microwave cavity 2 is less than half of the minimum value of the working wavelengths of all microwave sources 4 .

[0051] All microwave feed ports 7 are arranged on the inner bottom surface.

[0052] All the microwave feed ports 7 are rectangular waveguides, and the working mode is TE 10 model.

[0053] The wide sides of all the microwave feed ports 7 are perpendicular to the moving direction of the conveyor belt 5 , and the direction of the electric field in the microwave feed ports 7 is consistent with the moving direction of the conveyor belt 5 .

[0054] The technical problem to be solved by the present invention is: uniformity and high efficiency of the tunnel type microwave heating device. Figure 6 As shown, the existing microwave heating device is generally provided with a microwave feed port 7 at the top, and the transmission belt needs to carry the heated object through the microwave cavity 2. In order to ensure that the heated object and the transmission belt can pass through the microwave cavity 2 smoothly, the height of the microwave cavity 2 is generally set to be relatively large, greater than the working wavelength λ of the microwave source. Since the length and width of the microwave cavity 2 are generally much greater than the working wavelength λ of the microwave source, the microwave cavity 2 is a highly overmoded resonant cavity. When a microwave source feeds microwave energy into such a highly overmoded resonant cavity, many microwave modes can be excited at the same time, and the phases and amplitudes between various modes are difficult to determine using theoretical, numerical simulation and experimental methods. Therefore, in the prior art, the working mode in the microwave cavity 2 is difficult to determine, and the field distribution therein is uncertain, which ultimately leads to uneven heating of the heated object. To address this issue, a conventional approach is to add an extension to the microwave feed 7, extending it into the microwave cavity 2. For example, patent CN101282600A describes adding an extension (a flat-mouth horn unit) to the microwave feed 7. These microwave feeds 7 share the same microwave source, resulting in the microwaves output by the flat-mouth horn units coupling with each other and concentrating directly below them. However, this approach is difficult to achieve uniform heating due to the uneven distribution of the heated material.

[0055] like Figure 7 As shown, the technical solution of the present invention is based on reducing the height of the microwave cavity. Research has found that when the height of the microwave cavity is reduced to less than the operating wavelength λ, especially when it is reduced to less than the operating wavelength λ / 4 (taking 2450MHz as an example, its wavelength is 122mm, and the corresponding height is set to λ / 4 = 30.5mm), its mode can be better determined. At this time, a highly uniform electromagnetic field will appear near the microwave feed 7 (inside the microwave cavity). Therefore, in order to ensure that the heated object is heated as evenly as possible, given the downward curvature of the conveyor belt caused by natural gravity, if the microwave feed 7 is placed above, the heated object in the middle area of ​​the conveyor belt will easily move away from the microwave feed 7. Therefore, the present invention places the microwave feed 7 at the bottom and uses the bottom plate (inner bottom surface) to support the conveyor belt, so that the entire conveyor belt can maintain a high level. The heated object can be as close as possible to the end face of the microwave feed 7, that is, the heated object passes through the uniform area as much as possible. Therefore, the present invention combines the technical elements of reducing the thickness, arranging the microwave feed port 7 at the bottom, and running the transmission belt close to the bottom to achieve the goal of uniform heating of the heated object.

[0056] The technical solution of the present invention is based on reducing the height of the microwave cavity. Research has found that when the height of the microwave cavity is reduced to less than the operating wavelength λ, especially to less than λ / 4 of the operating wavelength, its mode can be better determined. At this point, since the volume of the heated object does not change, the volume of the microwave cavity (resonant cavity) is reduced, thereby increasing the proportion of the heated object in the microwave cavity. In other words, the heated object is filled in the resonant cavity at the highest possible ratio. At the same time, due to the losses of the heated object, the mutual coupling between different microwave feed ports is greatly reduced. This increase in the proportion of the heated object in the microwave cavity and the reduction in mutual coupling between different microwave feed ports enable the present invention to use a mixer to significantly improve the matching between each microwave source and the microwave cavity, thereby significantly improving the heating efficiency of the device. Specifically, each microwave source can be matched to the microwave cavity within the widest frequency band through the mixer. This facilitates the use of microwave sources with large frequency drift and wide frequency spectrum, such as magnetrons. Magnetrons can achieve microwave input with a wide frequency spectrum, which can improve the heating efficiency of the device.

[0057] Compared to the present invention, the prior art uses microwaves to heat the object within a highly overmoded microwave cavity with uncertain electromagnetic fields, resulting in poor heating uniformity. Furthermore, the mutual coupling between different microwave sources in the prior art is strong, making it impossible to use a mixer to match each microwave source to the microwave cavity. A large portion of the microwave energy is reflected back to the microwave source, resulting in wasted energy and damage to the microwave source. This results in low heating energy efficiency and high equipment operating costs due to the constant replacement of microwave sources. The present invention creates a deterministic and uniform electromagnetic field, and provides good isolation between different microwave sources, which improves microwave source matching and achieves uniform and efficient microwave heating and drying.

[0058] Example 2

[0059] like Figure 1 、 2 and 4.

[0060] The only difference between Example 2 and Example 1 is that the wide sides of all the microwave feed ports 7 are parallel to the moving direction of the conveyor belt 5 , and the direction of the electric field in the microwave feed ports 7 is perpendicular to the moving direction of the conveyor belt 5 .

[0061] Example 3

[0062] like Figure 5 shown.

[0063] The only difference between Example 3 and Example 1 is that the angle between the normal direction of any point on the inner bottom surface and the gravity direction is greater than 90 degrees and less than 180 degrees.

[0064] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. The main innovation of the present invention is: compressing the height of the microwave cavity to be less than the working wavelength of the microwave source, arranging all microwave sources on the bottom surface of the microwave cavity, placing the conveyor belt 5 close to the bottom surface of the microwave cavity, making the heated object as close to the microwave feed as possible, improving the certainty of the heating electromagnetic field, and using a mixer to adjust the microwave source and the resonant cavity to improve the heating efficiency of the equipment. At the same time, the top cover of the equipment can be easily opened, making it very easy to clean the interior. According to the technical essence of the present invention, within the spirit and principles of the present invention, any simple modification, equivalent replacement and improvement of the above embodiments are still within the scope of protection of the technical solution of the present invention.

Claims

1. A compact microwave tunnel furnace, comprising a microwave suppressor A (1), a microwave cavity (2), and a microwave suppressor B (3) connected in sequence, and at least one conveyor belt (5) for carrying a heated object (6) and driving the heated object (6) to move with its own movement, wherein the conveyor belt (5) passes through the microwave suppressor A (1), the microwave cavity (2), and the microwave suppressor B (3) in sequence, and the inner surface of at least one section of the microwave cavity (2) comprises an inner top surface, an inner bottom surface, an inner side surface A, and an inner side surface B; the inner top surface and the inner bottom surface are arranged opposite to each other, and the inner side surface A and the inner side surface B are arranged opposite to each other; and the characteristic is that: The invention also includes at least one microwave source (4), each microwave source (4) inputs microwave energy into the microwave cavity (2) through a corresponding microwave feed port (7), the microwave feed port (7) is arranged on the inner bottom surface, and the upper end of the microwave feed port (7) is arranged flush with the inner bottom surface, and the inner top surface is a part of a plane on which no microwave feed port (7) is arranged; the minimum value of the distance H between any point on the inner bottom surface and any point on the inner top surface of the microwave cavity (2) is less than or equal to the minimum value of the operating wavelength λ of all microwave sources (4); the conveyor belt (5) includes a carrying section for carrying the heated object (6), and the carrying section is in contact with the inner bottom surface of the microwave cavity (2).

2. A compact microwave tunnel furnace according to claim 1, characterized in that: The minimum value of the distance H between any point on the inner bottom surface and any point on the inner top surface of the microwave cavity (2) is less than or equal to half the minimum value of the operating wavelength λ of all microwave sources (4).

3. The compact microwave tunnel furnace according to claim 1, characterized in that: The minimum value of the distance H between any point on the inner bottom surface and any point on the inner top surface of the microwave cavity (2) is less than one quarter of the minimum value of the operating wavelength λ of all microwave sources (4).

4. A compact microwave tunnel furnace according to any one of claims 1 to 3, characterized in that: At least two microwave feed ports (7) are arranged on the inner bottom surface.

5. A compact microwave tunnel furnace according to any one of claims 1 to 3, characterized in that: All microwave feed ports (7) are arranged on the inner bottom surface.

6. The compact microwave tunnel furnace according to claim 1, characterized in that: The inner bottom surface is a part of a horizontal plane or the angle between the inner bottom surface and the horizontal plane is greater than 90 degrees and less than 180 degrees.

7. The compact microwave tunnel furnace according to claim 6, characterized in that: At least two of the microwave feed ports (7) are rectangular waveguides, wherein the working mode is TE 10 model.

8. The compact microwave tunnel furnace according to claim 6, characterized in that: All the microwave feed ports (7) are rectangular waveguides, and the working mode is TE 10 model.

9. The compact microwave tunnel furnace according to claim 8, characterized in that: The direction of the electric field in the microwave feed port (7) is consistent with the moving direction of the conveyor belt (5).

10. The compact microwave tunnel furnace according to claim 8, characterized in that: The direction of the electric field in the microwave feed port (7) is perpendicular to the moving direction of the conveyor belt (5).

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