Large-space environment control cavity with low-frequency electromagnetic shielding function

Abstract

The invention belongs to the technical field of environment control of precision equipment, and discloses a large-space environment control cavity with a low-frequency electromagnetic shielding function, and the outer side of the environment control cavity is provided with a composite heat preservation electromagnetic shielding plate to form a totally-enclosed structure; an inner cavity of the box body is divided into a top-layer chamber and an equipment chamber from top to bottom; an air inlet cavity and an air return cavity are arranged in the top-layer cavity, the air inlet cavity is connected with an air inlet, the air return cavity is connected with an air return opening, and the air inlet and the air return opening are respectively connected with the precise constant-temperature air conditioner; a plurality of four-corner air return openings are formed in the peripheral side of the equipment cavity and connected with the air return cavity through built-in hoses, an airflow system with top air supply and four-corner air return is formed, so that holes needed by airflow circulation are reduced, the cavity shields thermal disturbance of the external environment, meanwhile, heat and small particles generated by equipment in the equipment cavity are eliminated, and the heat efficiency of the equipment is improved. And the temperature stability and high cleanliness in the equipment chamber are maintained.

Description

Technical Field

[0001] The present invention relates to the field of environmental control of precision equipment, and particularly to an environmental control cavity with low-frequency electromagnetic shielding function in a large space. More specifically, it relates to a cavity for low-frequency electromagnetic shielding, maintaining high environmental cleanliness, and thermal disturbance shielding for an electron beam lithography machine. Background Art

[0002] An electron beam lithography machine mainly realizes fine pattern exposure by accelerating and focusing an electron beam to generate energy deposition on the material surface. It is mainly used for the production of small batches of chips and the manufacture of complex chip structures, with high flexibility. The focusing and deflection accuracy of the electromagnetic lens of the electron beam lithography machine will decrease due to the influence of temperature fluctuations. The positioning device laser interferometer of the precision motion workbench carrying the silicon wafer will also be affected by temperature fluctuations and tiny particles, resulting in positioning errors, thus affecting the imaging accuracy. There are the Earth's environmental magnetic field, electromagnetic radiation sources such as power equipment and wireless communication equipment in the external environment. Weak electromagnetic interference will cause the electron beam to deviate, resulting in pattern distortion or incorrect etching. At the same time, electromagnetic interference will also disrupt the focusing system of the electron beam, leading to blurred images and processing errors. Therefore, it is necessary to construct a high-precision electromagnetic protection, thermal protection, and high-cleanliness environmental control space outside the electron beam lithography machine to maintain the high-precision operation of the electron beam lithography machine.

[0003] In the prior art, the patent document CN219214321U describes an assembled thermal insulation electromagnetic shielding cabin. The plate material is composed of an inner and outer skin joined together, with foaming material filled in the middle. Both the inner and outer skins are carbon fiber materials, and a metal wire mesh is filled between the inner and outer skins for electromagnetic shielding and thermal insulation. The plate material is supported by a square frame and four corner columns. However, its carbon fiber structure is costly, and there are ventilation and cable holes, seriously affecting the electromagnetic shielding efficiency and unable to meet the electromagnetic shielding and thermal insulation requirements of precision equipment.

[0004] The patent document CN114412248A describes an electromagnetic shielding and thermal insulation machine room applied to communication equipment, mainly composed of a profile skeleton and inner and outer skins, with thermal insulation materials filled between the inner and outer skins. Its shielding window adopts a combination form of a shutter, a dust-proof net, a waveguide ventilation window, a ventilation device, and a metal protection net, which can reduce the loss of electromagnetic shielding efficiency caused by holes while retaining the ventilation function. However, its structure is complex, and the plate material composed of the inner and outer skins cannot be effectively expanded into a large-size electromagnetic shielding and thermal insulation space.

[0005] Existing electromagnetic shielding cavities with air circulation structures have a large number of air supply and return holes, which affect the electromagnetic shielding effectiveness; traditional large-size electromagnetic shielding plates are joined with gaps, which affect the electromagnetic shielding effectiveness; and the existing connection and fixing methods between electromagnetic shielding plates will reduce the integrity of the plates and lack compensation measures for the loss of electromagnetic shielding effectiveness caused by the connection methods. Therefore, there is an urgent need to design an environmental control cavity with low-frequency electromagnetic shielding function in a large space. Summary of the Invention

[0006] In view of the above defects or improvement requirements of the prior art, the present invention provides an environmental control cavity with low-frequency electromagnetic shielding function in a large space, thereby solving the technical problem of the loss of electromagnetic shielding effectiveness of traditional large-size electromagnetic shielding plates.

[0007] To achieve the above object, according to one aspect of the present invention, there is provided an environmental control cavity with low-frequency electromagnetic shielding function in a large space. A composite heat-insulating electromagnetic shielding plate is provided outside the environmental control cavity to form a fully enclosed structure; its inner cavity is divided into a top chamber and an equipment chamber from top to bottom; an air inlet cavity and a return air cavity are provided in the top chamber, the air inlet cavity is connected to an air inlet, the return air cavity is connected to a return air outlet, and the air inlet and the return air outlet are respectively connected to a precision constant temperature air conditioner; a plurality of four-corner return air outlets are provided on the periphery of the equipment chamber, and the four-corner return air outlets are connected to the return air cavity through an internal hose to form an air flow system of top air supply and four-corner return air, so as to reduce the holes required for air circulation.

[0008] Preferably, the environmental control cavity is composed of frame profiles spliced together, and the composite heat-insulating electromagnetic shielding plate is arranged inside the frame profiles.

[0009] Preferably, the frame profiles are formed into a cubic or cuboid frame structure through connectors, and return air columns are provided at the four corners of the side surface. The four-corner return air outlets are arranged on the side of the return air column facing the equipment chamber. The return air column and the composite heat-insulating electromagnetic shielding plate form a closed return air channel, and the return air channel is communicated with the return air cavity through an air duct to realize the air flow form of four-corner return air.

[0010] Preferably, the connectors include angle groove connectors, one-word connectors and whistle connectors to connect the frame profiles at angles, horizontally and vertically.

[0011] Preferably, a global filter is provided between the top chamber and the equipment chamber, and the global filter is supported by the wing edges of the frame profiles.

[0012] Preferably, an access door is provided on one side of the equipment chamber. The access door is formed by frame profiles, and a composite heat-insulating electromagnetic shielding plate is provided thereon.

[0013] Preferably, the composite heat-insulating electromagnetic shielding plate includes an inner permalloy layer, aluminum alloy pads, a heat-insulating plate layer, middle-shaped aluminum blocks, and an outer permalloy layer. The outer permalloy layer is arranged inside the frame profile. A heat-insulating plate layer is provided between the inner permalloy layer and the outer permalloy layer. The side of the heat-insulating plate layer is provided with a groove. One end of the middle-shaped aluminum block is inserted into the groove, and the other end is connected to the frame profile. The aluminum alloy pads are located between the heat-insulating plate layer and the inner permalloy layer.

[0014] Preferably, the inner permalloy layer includes a first inner permalloy plate and a second inner permalloy plate. The ends of the first inner permalloy plate and the second inner permalloy plate are respectively bent to partially overlap. The two bent overlapping areas overlap with each other to form a four-layer permalloy plate overlapping structure. The aluminum alloy pads are located inside the overlapping area of the inner permalloy plates, so that a first cavity is formed between the inner permalloy layer and the outer permalloy layer, effectively increasing the electromagnetic shielding efficiency.

[0015] Preferably, the overlapping thickness of the four-layer permalloy plate overlapping structure is 4 mm. Inner bolt connection holes are provided therein, and are fixed by bolts passing through the inner bolt connection holes and connecting with the frame profile. And the overlapping area should be greater than 1.38 times the cross-sectional area of the inner bolt connection holes to compensate for the magnetic flux loss of the reverse magnetic field in this area caused by the non-fully contacting connection of the bolt holes and the bolts.

[0016] Preferably, the outer permalloy layer includes a first outer permalloy plate and a second outer permalloy plate. The end of the first outer permalloy plate is U-shaped. The end of the second outer permalloy plate is bent and located on one side of the U-shaped opening to form a three-layer permalloy plate lapping structure, so as to form a second cavity between the first outer permalloy plate and the second outer permalloy plate, effectively increasing the electromagnetic shielding efficiency.

[0017] Preferably, the overlapping thickness of the three-layer permalloy plate lapping structure is 3 mm. Outer bolt connection holes are provided therein, and are fixed by bolts passing through the outer bolt connection holes and connecting with the frame profile. And the overlapping area should be greater than 1.64 times the cross-sectional area of the outer bolt connection holes to compensate for the magnetic flux loss of the reverse magnetic field in this area caused by the non-fully contacting connection of the bolt holes and the bolts.

[0018] Generally speaking, compared with the prior art by the above technical solution conceived by the present invention, the following beneficial effects are obtained:

[0019] (1) Adopt a fully enclosed environmental control cavity structure. The top chamber is provided with an air inlet chamber and a return air chamber. The four corners of the equipment chamber are supported by return air columns. The return air columns and the plates form a closed channel for air return, realizing the air flow form of supplying air from the top of the equipment chamber and returning air from the four corners, and reducing the holes required for air circulation; shield the thermal disturbance of the external environment, and at the same time remove the heat and fine particles generated by the equipment in the equipment chamber, maintaining the temperature stability and high cleanliness in the equipment chamber;

[0020] (2) Use composite thermal insulation electromagnetic shielding plates for splicing and sealing for electromagnetic protection. The composite thermal insulation electromagnetic shielding plate is a five-layer composite structure of permalloy - aluminum alloy - rock wool layer - aluminum alloy - permalloy. The inner and outer permalloy form two inner and outer permalloy cavities, and the volume ratio of the inner and outer permalloy cavities is less than 0.87;

[0021] (3) The permalloy plates overlap each other. The area of the 3-layer overlap area is more than 1.64 times the cross-sectional area of the bolt, and the area of the 4-layer overlap area is more than 1.38 times the cross-sectional area of the bolt to compensate for the loss of electromagnetic shielding efficiency caused by bolt connection. Description of the Drawings

[0022] Figure 1 is the structural schematic diagram of the environmental control cavity provided by the present invention after removing the composite plates;

[0023] Figure 2 is the internal structural schematic diagram of the environmental control cavity provided by the present invention;

[0024] Figure 3 is the overall structural appearance diagram of the environmental control cavity provided by the present invention;

[0025] Figure 4 is the cavity semi-sectional view of the environmental control cavity provided by the present invention;

[0026] Figure 5 is the partial structural schematic diagram of area E in the environmental control cavity provided by the present invention;

[0027] Figure 6 is the simplified partial structural schematic diagram of area E in the environmental control cavity provided by the present invention;

[0028] Figure 7 is the partial structural schematic diagram of area C in the environmental control cavity provided by the present invention;

[0029] Figure 8 is the partial structural schematic diagram of area D in the environmental control cavity provided by the present invention. Detailed Embodiments

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] Please refer to Figures 1-8 , a large-space environmental control cavity with low-frequency electromagnetic shielding function provided by the present invention includes a frame profile 1, a return air cavity 2, a return air outlet 3, an air inlet 4, an air inlet cavity 5, four-corner return air outlets 6, return air columns 7, an access door 8, an air duct 9, a global filter 10, a composite board 11, a cable through-hole 12, a bottom plate 13, a power switch 14, a top chamber 15 and an equipment chamber 16. A composite heat-insulating electromagnetic shielding board 11 is provided outside the environmental control cavity to form a fully enclosed structure; its inner cavity is divided into a top chamber 15 and an equipment chamber 16 from top to bottom; an air inlet cavity 5 and a return air cavity 2 are provided in the top chamber 15, and the air inlet cavity 5 and the return air cavity 2 are connected to the frame profile 1 by expansion bolts; the air inlet cavity 5 is connected to the air inlet 4, and the return air cavity 2 is connected to the return air outlet 3, and the air inlet 4 and the return air outlet 3 are respectively connected to a precision constant-temperature air conditioner; several four-corner return air outlets 6 are provided on the periphery of the equipment chamber 16, and the four-corner return air outlets 6 are connected to the return air cavity 2 through an internal hose to form an air flow system of top air supply and four-corner return air, so as to reduce the holes required for air flow circulation.

[0032] The environmental control cavity is composed of mutually spliced frame profiles 1, and the composite heat-insulating electromagnetic shielding board 11 is arranged inside the frame profile 1. The frame profile 1 forms a cubic or cuboid frame structure through connectors, and return air columns 7 are provided at the four corners of the side surface. The four-corner return air outlets 6 are arranged on the side of the return air column 7 facing the equipment chamber 16. The return air column 7 and the composite heat-insulating electromagnetic shielding board 11 form a closed return air channel, and the return air channel is communicated with the return air cavity 2 through an air duct 9 to realize the air flow form of four-corner return air. The connectors include angle groove connectors, one-word connectors and whistle connectors to connect the frame profiles 1 at angles, horizontally and vertically.

[0033] The internal space of the return air column 7 is a closed space formed by the four-corner column part of the frame profile 1 cooperating with the composite board 11, providing a closed channel for air flow return. Using the return air column 7 as the profile four-corner support component can reduce the number of parts generated during the installation and disassembly process, effectively reduce the assembly time and improve the assembly efficiency.

[0034] A global filter 10 is provided between the top chamber 15 and the equipment chamber 16, and the global filter 10 is supported by the flange of the frame profile 1. An access door 8 is provided on one side of the equipment chamber 16. The access door 8 is the only passage for staff to enter and exit during the shutdown of the equipment. The access door 8 is formed by the frame profile 1 and is provided with a composite thermal insulation electromagnetic shielding plate 11 thereon. The equipment cables enter and exit the environmental control cavity through the cable through-hole 12, and all the equipment cables are tightly wrapped by aluminum foil shielding sleeves to prevent the electromagnetic radiation of the cables from spreading into the environmental control cavity. The power switch 14 is the main power switch of the precision constant temperature air conditioner externally connected to the environmental control cavity.

[0035] The working mode of the environmental control cavity is as follows: The constant temperature air flow flows into the air inlet chamber 5 from the cavity air inlet 4 through the precision constant temperature air conditioner. Due to the wall resistance of the air inlet chamber 5, the constant temperature air flow is transformed from a large-flow air flow in the horizontal direction to a small-flow air flow in the vertical direction. Subsequently, the air flow flows into the top chamber 15 from the outlet of the air inlet chamber 5. Under the action of the wall resistance of the top chamber 15, the constant temperature air flow is homogenized in the top chamber 15 and flows downward to the global filter 10. Due to the resistance of the global filter 10, the constant temperature air flow will be homogenized and filtered again, realizing the uniform delivery of the constant temperature and clean air flow on the top plane of the equipment chamber 16. This air flow forms a laminar air bath form of temperature control and cleanliness control in the equipment chamber 16. This air flow form forms a global air bath environment in the equipment chamber 16 and cooperates with the composite plate 11 with high heat resistance to shield the thermal disturbance of the external environment. At the same time, it removes the heat and fine particles generated by the equipment in the equipment chamber 16, maintaining the temperature stability and high cleanliness in the equipment chamber 16. The four-corner air return openings 6 of the equipment cavity are arranged at the air return columns 7. The air flow flows into the air return channel formed by the air return column 7 and the composite plate 11 through the four-corner air return openings 6. The air flow flows through the outlet of the air return channel and into the air return cavity 2 through the air duct 9 for temperature filtering. Subsequently, the air flow flows into the externally connected precision constant temperature air conditioner through the air return opening 3 for re-temperature control, and the air flow with extremely high temperature stability is input into the environmental control cavity again for circulation.

[0036] The composite thermal insulation electromagnetic shielding plate 11 includes a permalloy inner layer, an aluminum alloy spacer 113, a thermal insulation plate layer 114, a middle-shaped aluminum block 115 and a permalloy outer layer. The permalloy outer layer is arranged on the inner side of the frame profile 1. A thermal insulation plate layer 114 is provided between the permalloy inner layer and the permalloy outer layer. The side of the thermal insulation plate layer 114 is provided with a groove. One end of the middle-shaped aluminum block 115 is inserted into the groove, and the other end is connected to the frame profile 1. The aluminum alloy spacer 113 is located between the thermal insulation plate layer 114 and the permalloy inner layer.

[0037] The composite thermal insulation electromagnetic shielding plate is a five-layer composite structure of Permalloy-Aluminum Alloy-Rock Wool Layer-Aluminum Alloy-Permalloy, wherein the single layer thickness of the Permalloy plate involved is 1mm, the Permalloy grade is 1J85, and the connecting bolts of the Permalloy plate are also made of Permalloy material with the grade of 1J85. The composite plate 11 is composed of an inner layer Permalloy plate 111, an inner layer Permalloy plate 112, an outer layer Permalloy plate 116, an outer layer Permalloy plate 117, a thermal insulation plate 114, an aluminum alloy pad 113, and a middle aluminum 115. Figure 5 Partial view of area E and Figure 6 The simplified partial view of region E is shown in the figure. The insulation board 114 is a board shell composed of a 1mm thick aluminum alloy board, and is filled with an integrated insulation board composed of 50mm thick rock wool. The insulation board 114 has a groove on the side, and is connected to the frame profile 1 with the middle aluminum 115, and a baffle is added on the outside for fixing. The calculation formula for the skin depth of the Permalloy board involved in the present invention, that is, the material thickness required to reduce the electric field and magnetic field intensity by 9dB, is as follows:

[0038]

[0039] Where f represents the electromagnetic frequency;

[0040] μ represents the electrical conductivity of the material, and the electrical conductivity of the Permalloy used in the present invention is 1500000 S / m;

[0041] σ represents the magnetic permeability of the material, and the initial relative magnetic permeability of the Permalloy used in the present invention is taken as 100000.

[0042] From the above formula, it is known that after the skin depth is determined, the thickness of the material is increased, and its electromagnetic shielding effectiveness increases linearly in dB. For the low-frequency electromagnetic shielding involved in the present invention, magnetic shielding is mainly performed. Its basic principle is that high magnetic permeability materials can excite corresponding reverse magnetic fields under the excitation of external magnetic fields according to Faraday's law of electromagnetic induction to offset the interference of the external magnetic field. In addition, in the bolt connection area, there is a loss of magnetic permeability caused by the incomplete contact between the bolt connection hole and the bolt, which reduces the magnetic flux of the reverse magnetic field generated in this area under the excitation of the external environmental magnetic field. According to the CST simulation results, it loses about 60% of the magnetic flux of the reverse magnetic field. Therefore, the present invention chooses to increase the overlapping area near the bolt connection hole, increase the magnetic flux of the reverse magnetic field in this area under the excitation of the external magnetic field to offset the loss of reverse magnetic field flux caused by the bolt connection, and the minimum overlapping area is:

[0043]

[0044] Where S 0 represents the cross-sectional area of ​​the bolt connection hole in the plane perpendicular to the plane wave magnetic field;

[0045] N represents the total number of overlapping layers in the overlapping region.

[0046] The inner permalloy layer includes a first inner permalloy plate 111 and a second inner permalloy plate 112. The ends of the first inner permalloy plate 111 and the second inner permalloy plate 112 are respectively bent to partially overlap, and the two sets of bent overlapping regions overlap with each other to form a four-layer permalloy plate overlapping structure F. The aluminum alloy spacer 113 is located inside the overlapping region of the inner permalloy plates, so that a first cavity is formed between the inner permalloy layer and the outer permalloy layer, effectively increasing the electromagnetic shielding effectiveness. The overlapping thickness of the four-layer permalloy plate overlapping structure is 4 mm, and it is provided with inner bolt connection holes, and is fixed by bolts passing through the inner bolt connection holes and connecting with the frame profile 1. Moreover, the overlapping area should be greater than 1.38 times the cross-sectional area of the inner bolt connection hole, that is, greater than 277 mm 2 , to compensate for the magnetic flux loss of the reverse magnetic field in this area caused by the non-fully contacting connection between the bolt hole and the bolt.

[0047] In the present invention, the overlapping area of the permalloy plates in the overlapping region F is designed to be 300 mm 2 . At the same time, adopting this overlapping structure can reduce the holes and seams generated by the plates in the traditional splicing method, and avoid the loss of the electromagnetic shielding effectiveness of the cavity caused by the holes and seams. In addition, the aluminum alloy spacer 113 is located between the second inner permalloy plate 112 and the thermal insulation plate 114, so that a cavity is formed between the second inner permalloy plate 112 and the outer permalloy layer, which can effectively increase the electromagnetic shielding effectiveness.

[0048] The outer permalloy layer includes a first outer permalloy plate 117 and a second outer permalloy plate 116. The end of the first outer permalloy plate 117 is U-shaped, and the end of the second outer permalloy plate 116 is bent and located on one side of the U-shaped opening to form a three-layer permalloy plate overlapping structure G, so as to form a second cavity between the first outer permalloy plate 117 and the second outer permalloy plate 116, effectively increasing the electromagnetic shielding effectiveness. The overlapping thickness of the three-layer permalloy plate overlapping structure is 3 mm, and it is provided with outer bolt connection holes, and is fixed by bolts passing through the outer bolt connection holes and connecting with the frame profile 1. Moreover, the overlapping area should be greater than 1.64 times the cross-sectional area of the outer bolt connection hole, that is, greater than 328 mm 2 , to compensate for the magnetic flux loss of the reverse magnetic field in this area caused by the non-fully contacting connection between the bolt hole and the bolt

[0049] In the present invention, the overlapping area of the permalloy plates at the overlapping region G is designed to be 350 mm 2 . The U-shaped structure at the end of the first outer permalloy plate 117 makes a cavity formed between the first outer permalloy plate 117 and the second outer permalloy plate 116, which can effectively increase the electromagnetic shielding effectiveness.

[0050] In the present invention, the permalloy sheet forms a gap between the inner and outer permalloy sheets through the spacer block and the U-shaped structure at the end of the sheet, thereby forming inner and outer layers of permalloy cavities. The total electromagnetic shielding effectiveness accumulates, and the accumulation effect is related to the volume ratio of the inner and outer permalloy cavities. The formula for the total shielding effectiveness is:

[0051]

[0052] In the formula, S 1 and S 2 respectively represent the electromagnetic shielding effectiveness of the inner and outer cavities acting alone; V 1 and V 2 respectively represent the volumes of the inner cavity and the outer cavity.

[0053] The requirement for the electromagnetic shielding effectiveness of the application scenario involved in the present invention is: under the interference of the low-frequency plane wave of the earth's ambient magnetic field with a frequency of 10 kHz as the main component, its electromagnetic shielding effectiveness should reach more than 60 dB. According to the industry experience data, the impact on the permalloy material caused by machining and assembly will cause its magnetic permeability to decrease by 20%. Therefore, for the cavity composed of a single-layer permalloy sheet with a thickness of 1 mm, its electromagnetic shielding effectiveness in the plane wave environment of 10 kHz is 15 dB.

[0054] The present invention adopts a double-layer cavity form. The outer permalloy cavity A and the inner permalloy cavity B are both cavities composed of permalloy sheets with a thickness of 1 mm. Therefore, according to the above formula calculation, to achieve an electromagnetic shielding effectiveness of 60 dB, the volume ratio of the inner permalloy cavity B to the outer permalloy cavity A in the environmental control cavity should reach below 0.87. The size of the outer permalloy cavity A involved in the present invention is 3400 mm (length) × 2500 mm (width) × 2800 mm (height). Therefore, the plate spacing between the inner permalloy cavity B and the outer permalloy cavity A is designed to be 100 mm, and the volume ratio of the inner permalloy cavity B to the outer permalloy cavity A is 0.86. Under this size specification, the electromagnetic shielding effectiveness of the environmental control cavity involved in the present invention reaches 61.5 dB, meeting the operating environment requirements of the electron beam lithography machine.

[0055] The splicing at the corner of the outer permalloy cavity A is as shown in Figure 7 the partial view of area C. The corner is spliced by the first permalloy side plate 118 and the second permalloy side plate 119. Both are plates with a U-shaped structure at the end. Their ends are in contact and are fastened with bolts, which can reduce the assembly difficulty and the machining accuracy required for the plates, and reduce the pores at the corner. The corner splicing of the inner permalloy cavity B is spliced with an integral L-shaped plate, and the splicing between it and the side permalloy plate adopts the same lap joint structure as that of the first permalloy inner plate 111 and the second permalloy inner plate 112.

[0056] The bottom plate is assembled as Figure 8 shown in the partial view of area D. Since the bottom electromagnetic shielding plate is only single-layer, the cavity bottom plate 13 is formed by overlapping the first permalloy bottom plate 131 and the second permalloy bottom plate 132, so that the thickness of the bottom permalloy plate is the same as the total thickness of the side. The permalloy plate 133 in contact with the bottom plate 13 is an L-shaped plate, and the end is in contact with the first permalloy bottom plate 131. The first permalloy bottom plate 131, the second permalloy bottom plate 132 and the permalloy plate 133 are grounded through gaskets and grounding bolts, which can effectively reduce the plate holes and seams generated by internal stress and improve the overall structural strength and stiffness of the cavity.

[0057] Those skilled in the art can easily understand that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A large-space environmental control cavity with low-frequency electromagnetic shielding function, characterized in that: A composite heat-insulating electromagnetic shielding plate (11) is provided on the outside of the environmental control cavity to form a fully enclosed structure; its inner cavity is divided into a top chamber (15) and an equipment chamber (16) from top to bottom; An air inlet cavity (5) and an air return cavity (2) are provided in the top chamber (15); the air inlet cavity (5) is connected to the air inlet (4), the air return cavity (2) is connected to the air return port (3), and the air inlet (4) and the air return port (3) are respectively connected to a precision constant temperature air conditioner; A plurality of four-corner return air vents (6) are arranged on the peripheral side of the equipment chamber (16), and the four-corner return air vents (6) are connected to the return air chamber (2) via built-in hoses to form an air flow system of top air supply and four-corner return air, thereby reducing the number of holes required for air circulation.

2. A large-space environmental control cavity with low-frequency electromagnetic shielding function as claimed in claim 1, characterized in that: The environmental control cavity is composed of frame profiles (1) spliced ​​together, and the composite thermal insulation electromagnetic shielding plate (11) is arranged on the inner side of the frame profile (1).

3. The large-space environmental control cavity with low-frequency electromagnetic shielding function as claimed in claim 2, characterized in that: The frame profile (1) is connected to form a cubic or rectangular frame structure, and return air columns (7) are provided at the four corners of the side surface. The return air ports (6) are provided on the side of the return air columns (7) facing the equipment chamber (16). The return air columns (7) and the composite thermal insulation electromagnetic shielding plate (11) form a closed return air channel, and the return air channel is connected to the return air cavity (2) through an air duct (9) to realize the air flow form of the four-corner return air.

4. The large-space environmental control cavity with low-frequency electromagnetic shielding function as claimed in claim 3, characterized in that: The connecting pieces include angle groove connecting pieces, straight connecting pieces and whistle connecting pieces, so as to connect the frame profile (1) at an angle, horizontally and vertically.

5. The large-space environmental control cavity with low-frequency electromagnetic shielding function as claimed in claim 1, characterized in that: A global filter (10) is provided between the top chamber (15) and the equipment chamber (16), and the global filter (10) is supported by the wing edge of the frame profile (1); an access door (8) is provided on one side of the equipment chamber (16), and the access door (8) is formed by the frame profile (1) and a composite thermal insulation electromagnetic shielding plate (11) is provided thereon.

6. A large-space environmental control cavity with low-frequency electromagnetic shielding function as claimed in any one of claims 1 to 5, characterized in that: The composite thermal insulation electromagnetic shielding plate (11) comprises a permalloy inner layer, an aluminum alloy pad (113), a thermal insulation plate layer (114), a center aluminum block (115) and a permalloy outer layer, wherein the permalloy outer layer is arranged on the inner side of a frame profile (1), a thermal insulation plate layer (114) is arranged between the permalloy inner layer and the permalloy outer layer, a groove is provided on the side of the thermal insulation plate layer (114), one end of the center aluminum block (115) is inserted into the groove, and the other end is connected to the frame profile (1), and the aluminum alloy pad (113) is located between the thermal insulation plate layer (114) and the permalloy inner layer.

7. The large-space environmental control cavity with low-frequency electromagnetic shielding function as claimed in claim 6, characterized in that: The permalloy inner layer comprises a first permalloy inner plate (111) and a second permalloy inner plate (112), the ends of the first permalloy inner plate (111) and the second permalloy inner plate (112) are respectively bent to partially overlap, and two groups of bent overlapping areas overlap each other to form a four-layer permalloy plate overlapping structure, and the aluminum alloy pad (113) is located inside the inner layer permalloy plate overlapping area, so that a first cavity is formed between the permalloy inner layer and the permalloy outer layer, thereby effectively increasing the electromagnetic shielding performance.

8. The large-space environmental control cavity with low-frequency electromagnetic shielding function as claimed in claim 7, characterized in that: The overlapping thickness of the four-layer Permalloy sheet overlapping structure is 4 mm, an inner bolt connection hole is provided therein, and bolts are passed through the inner bolt connection hole to connect and fix the structure with the frame profile (1), and the overlapping area is greater than 1.38 times the cross-sectional area of ​​the inner bolt connection hole, so as to compensate for the magnetic flux loss of the reverse magnetic field in this area caused by the incomplete contact connection between the bolt hole and the bolt.

9. The large-space environmental control cavity with low-frequency electromagnetic shielding function as claimed in claim 6, characterized in that: The permalloy outer layer comprises a first permalloy outer plate (117) and a second permalloy outer plate (116); the end of the first permalloy outer plate (117) is U-shaped, and the end of the second permalloy outer plate (116) is bent and located on one side of the U-shaped opening to form a three-layer permalloy plate overlap structure, so as to form a second cavity between the first permalloy outer plate (117) and the second permalloy outer plate (116), thereby effectively increasing electromagnetic shielding performance.

10. The large-space environmental control cavity with low-frequency electromagnetic shielding function as claimed in claim 9, characterized in that: The overlapping thickness of the three-layer Permalloy sheet overlap structure is 3 mm, and an external bolt connection hole is provided therein, and the structure is fixed to the frame profile (1) by bolts passing through the external bolt connection hole, and the overlapping area is greater than 1.64 times the cross-sectional area of ​​the external bolt connection hole, so as to compensate for the magnetic flux loss of the reverse magnetic field in this area caused by the incomplete contact connection between the bolt hole and the bolt.

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