Conductive housing, electromagnetic wave heating device, and sensor device

Abstract

A conductive housing (10) provided with a first shielding body (11) and a second shielding body (12), wherein the second shielding body (12) forms an electrically closed space with the first shielding body (11), and a conductive mesh (12A) of the second shielding body (12) has a shape in which a plurality of mesh cells are arranged so as to be surrounded by edges with straight lines having the same length.

Description

Conductive housing, electromagnetic wave heating device, and sensor device

[0001] The present disclosure relates to a conductive housing that is see-through and includes a conductive mesh that shields electromagnetic waves between the inside and outside of the housing, an electromagnetic wave heating device, and a sensor device.

[0002] Microwave ovens are known that have a perforated metal that is transparent and prevents electromagnetic waves from leaking from the inside of the housing to the outside. For example, the microwave oven shown in Patent Document 1 has a perforated metal in the center of the door panel to prevent microwaves from leaking from the center of the door panel.

[0003] JP 2014-081091 A

[0004] The inventors conducted extensive research into conductive mesh that prevents electromagnetic waves from leaking from inside a housing to the outside and found that when electromagnetic waves are incident on a conductive mesh, the conductive mesh is heated by an induced current, and as the temperature rises due to heating, the conductive mesh deteriorates (burning, melting, disconnection, etc.). If a conductive mesh is thick enough, the sheet resistance of the conductive mesh can be reduced, thereby suppressing the temperature rise of the conductive mesh. However, due to manufacturing constraints, it may not be possible to set the thickness of the conductive mesh to a certain value or greater.

[0005] Furthermore, even if the conductive mesh does not have a sufficient thickness, by reducing the aperture ratio of the conductive mesh, that is, by increasing the ratio of the conductor area to the area covered by the conductive mesh, the sheet resistance value can be reduced, thereby suppressing the temperature rise of the conductive mesh. However, reducing the aperture ratio of the conductive mesh impairs the transparency, that is, the see-through property, of the conductive mesh, which impairs visibility into the inside of the housing and makes it difficult to observe the inside of the housing.

[0006] In other words, for example, in applications involving shielding electromagnetic waves with high power density, such as those from microwave ovens, there is a trade-off between suppressing temperature rise in the conductive mesh and ensuring transparency while satisfying manufacturing constraints.

[0007] The present disclosure has been made in consideration of the above-mentioned points, and aims to provide a conductive housing that can suppress deterioration of a conductive mesh due to heating caused by electromagnetic waves.

[0008] The conductive housing according to the present disclosure comprises a conductive first shield having an opening, and a second shield having a conductive mesh formed of an array of multiple meshes surrounded by straight lines of the same length as the edges, the second shield being disposed in the opening of the first shield, the conductive mesh being electrically connected to the first shield, and forming an electrically closed space together with the first shield.

[0009] According to the present disclosure, by creating a conductive mesh in a shape in which meshes are arranged with straight lines of the same length as the edges, the difference between the maximum and minimum temperatures in the tracks surrounding the mesh can be reduced, thereby lowering the maximum temperature and suppressing deterioration of the conductive mesh due to temperature rise while maintaining visibility.

[0010] 1 is a cross-sectional view schematically showing an electromagnetic wave heating device according to embodiment 1; FIG. 2 is a front view of a main part of a conductive mesh (mesh regular quadrangle) in the electromagnetic wave heating device according to embodiment 1; FIG. 3 is an explanatory diagram showing the polarization direction of an incident electromagnetic wave when the meshes that are unit meshes of the conductive mesh are regular quadrangles; FIG. 4 is a diagram showing the simulation results of the temperature distribution in a line surrounding a mesh when an electromagnetic wave polarized in the X direction is incident on a regular quadrangle mesh when the meshes that are unit meshes of the conductive mesh are regular quadrangles with sides parallel to the X-axis and Y-axis; FIG. 5 is an explanatory diagram showing the polarization direction of an incident electromagnetic wave when the meshes that are unit meshes of the conductive mesh are regular hexagons; FIG. 6 is an explanatory diagram showing the polarization direction of an incident electromagnetic wave when the meshes that are unit meshes of the conductive mesh are equilateral triangles; FIG. 7 is a front view of a main part of a conductive mesh (mesh regular hexagon) in the electromagnetic wave heating device according to embodiment 1; FIG. 8 is a diagram showing the maximum temperature and the minimum temperature on the line surrounding the mesh in a mesh model of the conductive mesh; and FIG. 9 is an explanatory diagram schematically showing a sensor device according to embodiment 2.

[0011] Embodiment 1 An electromagnetic wave heating device according to embodiment 1 will be described with reference to Figures 1 to 8. The electromagnetic wave heating device according to embodiment 1 is a device for heating an object by irradiating the object with electromagnetic waves, such as a microwave oven or microwave heating device for cooking. Since the main components of these electromagnetic heating devices are the same, the following description will be given using a microwave oven as an example.

[0012] As shown in Fig. 1, the electromagnetic wave heating device according to the first embodiment includes a conductive housing 10, an electromagnetic wave generating unit 20, and an electromagnetic wave radiating unit 30. Fig. 1 schematically shows the conductive housing 10, the electromagnetic wave generating unit 20, and the electromagnetic wave radiating unit 30. The electromagnetic wave generating unit 20 and the electromagnetic wave radiating unit 30 are housed inside the conductive housing 10. Note that the electromagnetic wave generating unit 20 may be located outside the conductive housing 10. The conductive housing 10 has a first shielding body 11 and a second shielding body 12.

[0013] The first shield 11 has an opening 11a and is shaped like a conductive box. The first shield 11 has, for example, a rectangular parallelepiped shape and has the opening 11a on its front surface, which is one of its six surfaces. The first shield 11 is made of a conductive material such as carbon steel, special steel, or another alloy.

[0014] The second shield 12 is provided in the opening 11a of the first shield 11 and has a conductive mesh 12A located in the center and a holder (not shown) that holds the conductive mesh 12A. The second shield 12 is a door that is attached to the opening 11a of the first shield 11 in an openable and closable manner, and blocks the opening 11a of the first shield 11 when closed. The first shield 11 and the second shield 12 form a space 10a of the conductive housing 10. An object to be heated (not shown) is stored in the space 10a of the conductive housing 10. Figure 1 schematically shows the first shield 11 and the second shield 12.

[0015] The conductive mesh 12A is electrically connected to the first shielding body 11 and forms an electrically closed space together with the first shielding body 11, a so-called closed space, as the internal space 10a of the conductive housing 10. The electrical connection between the conductive mesh 12A and the first shielding body 11 does not mean that they are in contact at one point, but rather that they are connected by contact or capacitive coupling at a narrow distance that is sufficient to provide the ability to block electromagnetic waves.

[0016] For example, the first shielding body 11 and the conductive mesh 12A may be electrically connected by providing points of contact or capacitive coupling at intervals of 1 / 10 or less of the wavelength of the electromagnetic waves to be shielded, in this embodiment 1, the electromagnetic waves generated by the electromagnetic wave generating unit 20. Most typically, the conductive mesh 12A is electrically connected to the first shielding body 11 by contacting it with the first shielding body 11 around the entire periphery of the edge of the opening 11a of the first shielding body 11.

[0017] Furthermore, a conductive material that is not a mesh but is a solid area may be provided around the entire periphery or part of the edge of the conductive mesh 12A to facilitate electrical connection between the conductive mesh 12A and the first shielding body 11. The holder that holds the conductive mesh 12A covers the entire surface of the conductive mesh 12A and is in the shape of a flat plate made of a light-transmitting material such as inorganic glass or heat-resistant polyimide.

[0018] The first shielding body 11 and the conductive mesh 12A function as a so-called conductor shield that shields the electromagnetic waves radiated from the electromagnetic wave radiating portion 30 between the inside and outside of the space 10a of the conductive housing 10. That is, the electromagnetic waves radiated from the electromagnetic wave radiating portion 30 are confined within the space 10a of the conductive housing 10. Due to the reversibility of electromagnetic waves, the conductive mesh 12A prevents the electromagnetic waves radiated from the electromagnetic wave radiating portion 30 from leaking from the inside to the outside of the space 10a of the conductive housing 10, which also means that the conductive mesh 12A prevents electromagnetic waves from outside the space 10a of the conductive housing 10 from entering the space 10a of the conductive housing 10.

[0019] The electromagnetic wave generating unit 20 is, for example, a magnetron that generates electromagnetic waves. The electromagnetic wave generating unit 20 is controlled by a controller (not shown) housed inside the conductive housing 10. The electromagnetic wave emitting unit 30 radiates the electromagnetic waves from the electromagnetic wave generating unit 20 into the space 10a of the conductive housing 10, thereby heating an object to be heated housed in the space 10a of the conductive housing 10. The electromagnetic wave emitting unit 30 is, for example, formed of an antenna that radiates electromagnetic waves. Note that the electromagnetic wave emitting unit 30 may also be formed of an opening of a waveguide that radiates the electromagnetic waves generated by the electromagnetic wave generating unit 20.

[0020] The conductive mesh 12A has an arrangement of meshes 12a, each surrounded by straight lines of the same length as its sides. As shown in the enlarged front view of a main part of the conductive mesh 12A in Fig. 2, the meshes 12a are square-shaped and surrounded by lines 12b, and the meshes 12a are arranged in the X-Y axis direction, i.e., in a lattice pattern.

[0021] Each mesh 12a is a regular rectangle with a side length a, and the line width of the lines 12b is the same throughout. The length of the diagonal line of each mesh 12a is equal to or less than the wavelength of the electromagnetic wave incident on the conductive mesh 12A and is longer than the wavelength of visible light. The length a of one side is also longer than the wavelength of visible light. The X-axis is the left-right direction, the Y-axis is the up-down direction, and the Z-axis is the front-back direction.

[0022] As will be described in detail later, the mesh 12a may be a regular hexagon as shown in Fig. 5 or an equilateral triangle as shown in Fig. 6. In short, the shape of the mesh 12a may be a regular n-gon surrounded by straight lines of equal length as sides, where n is a natural number of 3 or more. The mesh 12a ensures transparency of the conductive mesh 12A, and the lines 12b surrounding the mesh 12a shield electromagnetic waves.

[0023] The maximum distance between sides surrounding each mesh 12a in the conductive mesh 12A is equal to or less than the wavelength of the electromagnetic waves incident on the conductive mesh 12A, which in the first embodiment is the electromagnetic waves radiated from the electromagnetic wave radiating portion 30, and the minimum distance is longer than the wavelength of visible light. When the shape of the mesh 12a is a regular square, the length of the diagonal is equal to or less than the wavelength of the electromagnetic waves, and the length a of one side is longer than the wavelength of visible light.

[0024] When the shape of the mesh 12a is a regular hexagon, the length of the line segments connecting the opposing corners is equal to or shorter than the wavelength of the electromagnetic wave, and the distance between the opposing sides is longer than the wavelength of visible light.When the shape of the mesh 12a is an equilateral triangle, the length of the sides is equal to or shorter than the wavelength of the electromagnetic wave, and the length of the perpendicular lines is longer than the wavelength of visible light.

[0025] Next, we will explain the behavior of electromagnetic waves when they are incident on the conductive mesh 12A. When electromagnetic waves are incident on a conductor with a directional component parallel to the polarization direction of the electromagnetic waves, a current parallel to the polarization direction is induced in the conductor. For example, for the square mesh 12a shown in Figure 2, if the polarization direction of the electromagnetic waves is parallel to the X axis, a current is induced in the line 12b in the X axis direction, and if the polarization direction of the electromagnetic waves is parallel to the Y axis, a current is induced in the line 12b in the Y axis direction. Furthermore, if the polarization of the electromagnetic waves is tilted from the Y direction to the X direction in the X-Y plane, a current is induced in both the line 12b in the X axis direction and the line 12b in the Y axis direction. This is because the polarization direction of the electromagnetic waves has both an X direction component and a Y direction component.

[0026] Now, if the angle between the X-axis and the polarization direction of the electromagnetic wave is θ and the amplitude of the incident electric field is 1, the amplitude of the X component of the electric field due to the electromagnetic wave is cos θ and the amplitude of the Y component is sin θ. In other words, the current induced in line 12b is proportional to the electric field amplitude, and the strongest current is induced when the polarization direction of the electromagnetic wave and the direction of line 12b are parallel, and ideally no current is induced when they are perpendicular. When a current is induced in line 12b, power is consumed as heat due to the electrical resistance of line 12b, and the temperature of line 12b rises.

[0027] Based on the above considerations, the inventors performed a numerical simulation of the heat (temperature distribution) of the lines 12b surrounding the mesh 12a when electromagnetic waves are incident on the conductive mesh 12A. The numerical simulation was performed for the square mesh 12a shown in Figure 2, with the polarization of the electromagnetic waves parallel to the X-axis as shown in Figures 3 and 4. Figures 3 and 4 show only one mesh 12a, i.e., a unit mesh. The results of the numerical simulation are shown in Figure 4.

[0028] The temperature distribution shown in Fig. 4 is the temperature distribution on the lines 12b in the unit mesh of the conductive mesh 12A after a certain time has passed when an electromagnetic field polarized in the X direction is incident on the conductive mesh 12A. As can be seen from Fig. 4, the temperature of the lines 12b parallel to the X axis direction is high and the temperature of the lines 12b parallel to the Y axis direction is low. Furthermore, the center of the lines 12b in the X axis direction has the highest temperature, and the center of the lines 12b in the Y axis direction has the lowest temperature.

[0029] This is because heat is transferred from the X-axis direction line 12b to the Y-axis direction line 12b via the node 12c where the X-axis direction line 12b and the Y-axis direction line 12b intersect, i.e., the vertex of a regular square. The maximum temperature measured at the center of the X-axis direction line 12b was 236.2°C, and the minimum temperature measured at the center of the Y-axis direction line 12b was 182.3°C. The difference between the maximum and minimum temperatures was small, at 53.9°C, which resulted in a uniform temperature distribution in the line 12b. As a result, the maximum temperature was suppressed, improving the power durability of the conductive mesh 12A.

[0030] In the microwave oven for cooking to which the first embodiment is directed, the direction of radiation of electromagnetic waves from electromagnetic wave radiating unit 30 is rotated to eliminate uneven heating of an object to be heated placed within space 10a of conductive casing 10. For example, if electromagnetic wave radiating unit 30 is configured with an antenna, the antenna is rotated to change the electric field distribution within space 10a of conductive casing 10 over time. The electric field distribution within space 10a of conductive casing 10 also changes depending on the size and position of the object to be heated placed within space 10a of conductive casing 10. As a result, the polarization direction of the electromagnetic waves incident on conductive mesh 12A changes in various ways, and the values ​​of the currents induced in line 12b in the X-axis direction and line 12b in the Y-axis direction also change in various ways.

[0031] In the conductive mesh 12A, the lengths of the lines 12b on all four sides surrounding the mesh 12a are the same, so that the temperature rise in the lines 12b can be suppressed regardless of the polarization direction of the incident electromagnetic wave, and the temperature of the central part of the line 12b on the side parallel to the polarization direction of the incident electromagnetic wave does not rise extremely, thereby improving the power resistance of the conductive mesh 12A.

[0032] Furthermore, in the conductive mesh 12A, the line width of the line 12b is the same throughout the entire area, so the line width of the line 12b is the same for various polarization directions of the incident electromagnetic waves, and the temperature does not rise extremely depending on the position of the line 12b, thereby improving the power resistance of the conductive mesh 12A.

[0033] That is, even if the line width is narrowed to reduce the aperture ratio of the conductive mesh 12A, i.e., without reducing the see-through performance, in other words, even if the transparency is improved, by making the lengths of the lines 12b surrounding the mesh 12a all the same and making the line width the same across the entire area, the temperature distribution in the lines 12b constituting the conductive mesh 12A can be made uniform with the maximum temperature on the conductive mesh 12A reduced, even if the polarization direction of the incident electromagnetic wave changes in various ways. As a result, the conductive mesh 12A does not deteriorate due to burnout or the like.

[0034] The inventors also conducted simulations to verify the relationship between the size of the mesh 12a and the temperature distribution. When the regular square shape of the mesh 12a was expanded similarly, it was found that the larger the mesh 12a, the higher the maximum temperature and the lower the minimum temperature. This is because the temperature in the central area becomes more difficult to move as the node 12c, where the X-axis line 12b and the Y-axis line 12b intersect, moves away from the center of the side.

[0035] For this reason, if the conductive mesh 12A is not a regular square, but for example, if one of the four sides is longer than the other three sides, the highest temperature will appear on the longer side, which will be higher than the highest temperature if all four sides are the same length. As a result, the longer side will be more susceptible to deterioration due to burnout, etc., and the power resistance of the conductive mesh 12A will be reduced.

[0036] Conversely, when the square shape of the mesh 12a is scaled down in a similar manner, the smaller the size of the mesh 12a, the lower the maximum temperature and the higher the minimum temperature. In other words, the smaller the size of the square shape of the mesh 12a, the more uniform the temperature distribution in the lines 12b of the conductive mesh 12A tends to be. This is because the temperature in the central area tends to move more easily as the node 12c where the X-axis line 12b and the Y-axis line 12b intersect approaches the center of the side. Note that even if the square shape of the mesh 12a is scaled up or down in a similar manner, the aperture ratio per unit area does not change, so the transparency is comparable.

[0037] As can be seen from the above, the shorter the side length of the mesh 12a of the conductive mesh 12A, the more uniform the temperature distribution in the lines 12b that make up the conductive mesh 12A. In other words, since the maximum temperature in the lines 12b that make up the conductive mesh 12A is suppressed, deterioration of the conductive mesh 12A can be more effectively prevented even when electromagnetic waves with high power density are incident on the conductive mesh 12A. In other words, the power resistance of the conductive mesh 12A and the conductive housing 10 to which it is applied can be further improved.

[0038] In the first embodiment, the high power density of the electromagnetic wave is 1 mW / cm ２ The Association of Radio Industries and Businesses' standard for radio wave protection, RCR STD-38, states that the power density in a general environment, 1.5 GHz to 300 GHz, is 1 mW / cm ２ is set as the upper limit, so 1 mW / cm ２ A power density above this level is considered to be a high power density.

[0039] In addition, the household microwave oven has a high-frequency output of 500 W in the electromagnetic wave generating unit 20, and an area of ​​the electromagnetic shield provided in the door portion corresponding to the conductive mesh 12A is 500 cm. ２ (=25 cm × 20 cm), and if all of the electromagnetic waves radiated by the electromagnetic wave radiating portion 30 are irradiated evenly onto the electromagnetic shield, the power density of the electromagnetic waves incident on the electromagnetic shield will be 1000 mW / cm ２The conductive mesh 12A has a power density of 1000 mW / cm ２ Not only electromagnetic waves with a power density of 1 mW / cm ２ Blocks the above electromagnetic waves.

[0040] In the above example, the shape of the mesh 12a is a regular square, but for the following reason, it is not limited to a regular square, and the shape of the mesh 12a may be any regular n-gon surrounded by straight lines of equal length as sides, where n is a natural number greater than or equal to 3. In other words, it is known that among n-gons with a constant perimeter, a regular n-gon has the largest area.

[0041] In the conductive mesh 12A, when the lines 12b surrounding one mesh 12a are defined as a unit mesh, and all of the lines 12b arranged on each side of the lines 12b constituting the unit mesh have the same length and width, if the occupied area of ​​the conductive mesh 12A is the same, then among n-gons, the shape of the mesh 12a that has the largest area is a regular n-gon. In other words, by making the shape of the mesh 12a in the conductive mesh 12A, in which the meshes 12a are closely spaced vertically and horizontally in a plane to form a geometric pattern, the opening ratio of the conductive mesh 12A due to the mesh 12a, be a regular n-gon.

[0042] For example, if the mesh 12a is an n-gon, such as a rhombus, with unequal interior angles and equal sides, the length of each side must be increased to obtain the same opening area as a regular square. Therefore, under the condition that the opening ratio (= sheet resistance) of the conductive mesh 12A is the same, by making the mesh 12a a regular n-gon, the length of each side can be minimized compared to mesh 12a that is not a regular n-gon, resulting in the most uniform temperature distribution in the lines 12b surrounding the mesh 12a. In short, by making the mesh 12a a regular n-gon, with straight lines of equal length as the sides, the power resistance of the conductive mesh 12A can be improved.

[0043] The inventors further investigated the shape of the mesh 12 a and found that, from the viewpoint of the power resistance of the conductive mesh 12 A, a regular hexagon, a regular square, or a regular triangle is preferable for the shape of the mesh 12 a, and a regular hexagon is particularly preferable. In other words, the mesh 12 a of regular hexagons, regular squares, or regular triangles can be evenly distributed across the plane of the conductive mesh 12 A, and good results can be obtained in terms of the opening ratio and temperature distribution of the conductive mesh 12 A.

[0044] In particular, when the line width and aperture ratio of the lines 12b are the same, by making the shape of the mesh 12a a regular hexagon, the length of each side of the mesh 12a is the shortest, and the temperature distribution in the lines 12b surrounding the mesh 12a is most uniform. Figure 7 shows a front view of the main part of a conductive mesh 12A whose mesh 12a is a regular hexagon with a side length of b (<a).

[0045] Taking this into consideration, the inventors performed a numerical simulation of heat (temperature distribution) in the lines 12b surrounding the mesh 12a when electromagnetic waves are incident on the conductive mesh 12A, not only for the case where the shape of the mesh 12a is a regular square but also for the cases where the shape of the mesh 12a is a regular hexagon and a regular triangle. The numerical simulation was performed on a unit mesh model in which the line width and line thickness of the lines 12b are the same for each shape of the mesh 12a, and the size of the mesh 12a is set so that the sheet resistance value of the conductive mesh 12A is the same.

[0046] Under the conditions where the temperature of one side of the line 12b surrounding the mesh 12a rises the most, that is, an electromagnetic field (electromagnetic wave) having an electromagnetic wave polarized parallel to the Y-axis as shown in Figure 5 for a unit mesh model where the shape of the mesh 12a is a regular hexagon, and an electromagnetic wave having an electromagnetic wave polarized parallel to the X-axis as shown in Figure 6 for a unit mesh model where the shape of the mesh 12a is an equilateral triangle, was incident perpendicular to the plane of the unit mesh, and a numerical simulation was performed of the temperature distribution in the line 12b of the unit mesh after a certain period of time had passed.

[0047] The maximum and minimum temperatures of the line 12b in the unit mesh model obtained by numerical simulation of the temperature distribution are shown in Fig. 8. The results of the numerical simulation shown in Fig. 8 were obtained using a unit mesh model with a line width of 7.5 µm in the entire region.

[0048] In a model in which the shape of the mesh 12a is a regular hexagon, the maximum temperature was 231.5°C, the minimum temperature was 197.4°C, and the difference between the maximum and minimum temperatures was 34.1°C. In a model in which the shape of the mesh 12a is a regular triangle, the maximum temperature was 239.7°C, the minimum temperature was 190.7°C, and the difference between the maximum and minimum temperatures was 49.0°C. When the line width was 10 μm, similar results were obtained for the maximum and minimum temperatures.

[0049] As can be seen from Figure 8, the model with a regular hexagonal unit mesh had the lowest maximum temperature, and the temperature distribution in the unit mesh line 12b was also uniform. Note that, although the minimum temperature is also high due to the uniform temperature distribution, partial peeling of the conductive mesh 12A from the holder that holds it and deformation of the conductive mesh 12A, which are preliminary stages of deterioration such as burning, melting, and disconnection of the conductive mesh 12A, are caused by expansion and deformation of the conductive mesh 12A and the holder at the point where the maximum temperature is reached. Therefore, lowering the maximum temperature and uniforming the temperature distribution improves the power durability of the conductive mesh 12A.

[0050] As described above, the conductive housing 10 in the electromagnetic wave heating device according to embodiment 1 has a shape in which the conductive mesh 12A in the second shield 12, which forms an electrically closed space between itself and the first shield 11, is arranged in a plurality of meshes, each surrounded by straight lines of the same length as its edges. This makes it possible to make the temperature distribution in the lines 12b surrounding the mesh 12a uniform, thereby lowering the maximum temperature in the lines 12b and improving the power resistance of the conductive mesh 12A.

[0051] By improving the power resistance of the conductive mesh 12A, the power resistance of the conductive housing 10 is also improved. ２Even if the line width of the lines 12b constituting the conductive mesh 12A is narrowed to increase the aperture ratio, i.e., the transparency is improved, without the electromagnetic waves of the above power density leaking outside the conductive housing 10, the temperature distribution in the lines 12b can be made uniform with the maximum temperature on the conductive mesh 12A lowered, so that the conductive mesh 12A does not deteriorate due to burnout, etc. Furthermore, in the electromagnetic wave heating device, the conductive mesh 12A to which electromagnetic waves from the electromagnetic wave radiating unit 30 are incident with a high power density can have improved power resistance without impairing the transparency.

[0052] Second Embodiment A sensor device according to a second embodiment will be described with reference to Fig. 9. The sensor device according to the second embodiment is a sensor device that is attached to, for example, a manned or unmanned vehicle, a flying object including an aircraft, a ship, or the like. The main components of these sensor devices are the same, so the description will be given without making any particular distinction between them.

[0053] The sensor device according to the second embodiment includes a conductive housing 100, a sensor element 200, and a sensor processing device 300. Fig. 9 schematically shows the conductive housing 100, the sensor element 200, and the sensor processing device 300. The conductive housing 100 has a first shield 110 and a second shield 120.

[0054] The first shielding body 110 has an opening 110a and is a conductive structure. When the sensor device is a sensor device mounted on an air vehicle or a ship, the first shielding body 110 may share a part or the whole of the conductive structure of the air vehicle or the ship. The first shielding body 110 is formed of a conductive material such as carbon steel, special steel, or other alloy.

[0055] The second shield 120 is provided in the opening 110a of the first shield 110, and has a conductive mesh 120A and a holder (not shown) that holds the conductive mesh 120A. The peripheral edge of the holder is attached to the peripheral edge of the opening 110a of the first shield 110. The first shield 110 and the second shield 120 form a space 100a in the conductive housing 100.

[0056] The sensor element 200 and the sensor processing device 300 are housed in a space 100a of the conductive housing 100. Fig. 9 schematically shows the first shield 11 and the second shield 12. The conductive mesh 120A is electrically connected to the first shield 110 and forms an electrically closed space together with the first shield 110, a so-called closed space, as the internal space 100a of the conductive housing 100.

[0057] The electrical connection between the conductive mesh 120A and the first shielding body 110 is not limited to the electrical connection achieved by contacting the conductive mesh 120A with the first shielding body 110 around the entire periphery of the edge of the opening 110a of the first shielding body 110, as described in the first embodiment, but also includes connection by contact or capacitive coupling at a narrow interval that is sufficient to provide the ability to block electromagnetic waves incident on the conductive mesh 120A from outside the conductive housing 100. The electromagnetic waves that are incident on the conductive mesh 120A from outside the conductive housing 100 and are blocked here are so-called radio waves, which have longer wavelengths than infrared rays, when the sensor element 200 is an infrared camera.

[0058] The holder for holding the conductive mesh 12A is a flat plate made of a light-transmitting material such as inorganic glass or heat-resistant polyimide, and covers the entire surface of the conductive mesh 12A. The first shield 110 and the conductive mesh 120A function as a so-called conductor shield, preventing electromagnetic waves from entering the space 100a of the conductive housing 100 from the outside of the conductive housing 100, that is, shielding electromagnetic waves between the outside of the conductive housing 100 and the space 100a of the conductive housing 100.

[0059] Specifically, for example, when a lightning strike generates a high-intensity electromagnetic pulse, the high-intensity electromagnetic pulse penetrates the interior of the conductive housing 100, and in order to prevent the sensor element 200 arranged inside the conductive housing 100 from being destroyed by the high-intensity electromagnetic pulse, the first shielding body 110 and the conductive mesh 120A form a shield structure that blocks electromagnetic waves from entering the space 100a of the conductive housing 100 from outside the conductive housing 100.

[0060] The sensor element 200 is a sensor element that uses visible light or infrared light to capture an image of the outside of the space 100a from inside the space 100a of the conductive housing 100 through the conductive mesh 120A, and is typically a visible light camera or an infrared camera. When the sensor element 200 is a visible light camera, the first shielding body 110 and the conductive mesh 120A function as a conductive shield against electromagnetic waves with wavelengths longer than those of visible light, and when the sensor element 200 is an infrared camera, they function as a conductive shield against radio waves, which are electromagnetic waves with wavelengths longer than those of infrared light.

[0061] The sensor element 200 is disposed so that its lens faces the conductive mesh 120A and is housed within the space 100a of the conductive housing 100. The information acquisition section of the sensor element 200, which includes a lens, receives visible light or infrared light that has passed through the conductive mesh 120A, and acquires information from outside the space 100a of the conductive housing 100. The sensor element 200 senses, i.e., captures an image of, a subject outside the space 100a of the conductive housing 100. The external information acquired by the sensor element 200 is, for example, visual information.

[0062] The external information acquired by the sensor element 200 is processed by the sensor processing device 300 and stored in a storage device (not shown) or transmitted to another device (not shown) by wire or wirelessly. The sensor processing device 300 is housed in the space 100a of the conductive casing 100 and is electrically connected to the sensor element 200 by a cable 400. It is sufficient that the sensor processing device 300 is electrically connected to the sensor element 200 by the cable 400, and it may also be disposed outside the space 100a of the conductive casing 100.

[0063] Since the sensor element 200 and the cable 400 are housed within the space 100a of the conductive housing 100, which functions as a conductor shield, they are not exposed to electromagnetic waves from outside the space 100a of the conductive housing 100. There is no risk that a large current will be induced when the sensor element 200 and the cable 400 are exposed to electromagnetic waves, and that the induced large current will destroy the semiconductor components and electronic circuits that make up the sensor element 200 and the sensor processing device 300.

[0064] Similar to the conductive mesh 12A in the first embodiment, the conductive mesh 120A has an array of meshes, each surrounded by straight lines of the same length as its sides. The mesh shape is a regular n-gon, each surrounded by straight lines of the same length as its sides, where n is a natural number of 3 or greater. From the viewpoint of the power resistance of the conductive mesh 120A, it is preferable that the mesh shape be a regular hexagon, a regular square, or an equilateral triangle, with a regular hexagon being particularly preferable.

[0065] The maximum distance between sides surrounding each mesh in the conductive mesh 120A is equal to or less than the wavelength of the electromagnetic wave incident on the conductive mesh 120A from outside the conductive housing 100, and the minimum distance is longer than the wavelength of either visible light or infrared light. When the shape of the mesh 12a is a regular square, the length of the diagonal is equal to or less than the wavelength of the electromagnetic wave, and the length a of one side is longer than the wavelength of either visible light or infrared light.

[0066] When the shape of the mesh 12a is a regular hexagon, the length of the line segments connecting the opposing corners is equal to or less than the wavelength of the electromagnetic wave, and the distance between the opposing sides is longer than the wavelength of either visible light or infrared light.When the shape of the mesh 12a is an equilateral triangle, the length of the sides is equal to or less than the wavelength of the electromagnetic wave, and the length of the perpendicular lines is longer than the wavelength of either visible light or infrared light.

[0067] That is, conductive mesh 120A transmits visible light or infrared light but blocks electromagnetic waves with wavelengths longer than those of visible light or infrared light. Therefore, when sensor element 200 is a visible light camera, conductive mesh 120A blocks electromagnetic waves longer than the wavelength of visible light but passes visible light, so that the visible light camera can achieve its original purpose of capturing an image of a subject outside space 100a of conductive casing 100 via conductive mesh 120A, and the visible light camera and the cable connected to the visible light camera are not exposed to electromagnetic waves from outside space 100a of conductive casing 100, so there is no risk of damage to the semiconductor components and electronic circuits that make up visible light camera and sensor processing device 300.

[0068] Furthermore, when the sensor element 200 is an infrared camera, the conductive mesh 120A blocks radio waves, which are electromagnetic waves with wavelengths longer than those of infrared rays, and allows infrared rays to pass through. Therefore, the infrared camera can achieve its original purpose of photographing a subject outside the space 100a of the conductive housing 100 through the conductive mesh 120A, and the infrared camera and the cable connected to the infrared camera are not exposed to electromagnetic waves from outside the space 100a of the conductive housing 100, so there is no risk of the semiconductor components and electronic circuits that make up the infrared camera and sensor processing device 300 being destroyed.

[0069] Furthermore, since the mesh shape of the conductive mesh 120A is a regular n-polygon, when electromagnetic waves from outside the space 100a of the conductive housing 100 are incident on the conductive mesh 120A, even if a current is induced in the lines that make up the conductive mesh 120A by the electromagnetic waves and the temperature of the lines rises, as described in embodiment 1, the temperature distribution in the lines that make up the conductive mesh 120A is made uniform, the maximum temperature can be reduced, and the power resistance of the conductive mesh 120A is improved.

[0070] As described in the first embodiment, the shape of the mesh is preferably a regular hexagon, a regular square, or an equilateral triangle, with a regular hexagon being particularly preferable. When the line width was 7.5 μm, the same results as those shown in FIG. 8 were obtained for the maximum and minimum temperatures, and similar results were also obtained when the line width was 10 μm or less.

[0071] As described above, the conductive housing 100 in the sensor device according to embodiment 2 has a shape in which the conductive mesh 120A in the second shielding body 120, which forms an electrically closed space between itself and the first shielding body 110, is arranged in a plurality of meshes, each surrounded by straight lines of the same length as its edges. This makes it possible to uniformize the temperature distribution in the lines surrounding the mesh, reduce the maximum temperature in the lines, and improve the power resistance of the conductive mesh 120A.

[0072] Improving the power resistance of the conductive mesh 120A also improves the power resistance of the conductive casing 100. Furthermore, in the sensor device, the sensor element 200 can acquire information outside the space 100a of the conductive casing 100 via the conductive mesh 120A, and furthermore, electromagnetic waves incident on the conductive mesh 120A from outside the space 100a of the conductive casing 100 are prevented from entering the space 100a of the conductive casing 100, thereby preventing damage to the semiconductor components and electronic circuits constituting the sensor element 200 and the sensor processing device 300 due to electromagnetic waves from outside the space 100a of the conductive casing 100.

[0073] Any of the components in the embodiments may be modified or omitted.

[0074] The conductive casing according to the present disclosure can be applied to conductive casings in devices for heating an object to be heated by irradiating the object with electromagnetic waves, such as microwave ovens and microwave heating devices for cooking, and to conductive casings in sensor devices with built-in cameras.

[0075] 10 Conductive housing, 10a Space, 11 First shield, 11a Opening, 12 Second shield, 12A Conductive mesh, 12a Mesh, 12b Line, 20 Electromagnetic wave generating unit, 30 Electromagnetic wave emitting unit, 100 Conductive housing, 100a Space, 110 First shield, 110a Opening, 120 Second shield, 120A Conductive mesh, 200 Sensor element, 300 Sensor processing device.

Claims

1. A conductive housing comprising: a first conductive shield having an opening; and a second shield having a conductive mesh in the form of an array of multiple meshes surrounded by straight lines of the same length as each other, the second shield being disposed in the opening of the first shield, the conductive mesh being electrically connected to the first shield, and forming an electrically closed space together with the first shield.

2. The conductive casing according to claim 1, wherein the second shielding body has a light-transmitting holder that holds the conductive mesh.

3. The conductive case according to claim 2, wherein the support is made of inorganic glass or heat-resistant polyimide.

4. The conductive casing according to claim 1, wherein the shape of each mesh in the conductive mesh is a regular n-sided polygon (n is a natural number of 3 or more).

5. The conductive casing according to claim 1, wherein the shape of each mesh in the conductive mesh is any one of a regular hexagon, a regular square, and a regular triangle.

6. The conductive casing according to claim 1, wherein the shape of each mesh in the conductive mesh is a regular hexagon.

7. A conductive housing as described in claim 1, wherein the maximum distance between the sides surrounding each mesh in the conductive mesh is equal to or less than the wavelength of the electromagnetic wave incident on the conductive mesh, and the minimum distance is longer than the wavelength of either visible light or infrared light.

8. A conductive casing according to claim 1, wherein the lines surrounding each mesh in the conductive mesh have the same line width over the entire area.

9. An electromagnetic wave heating device comprising: a conductive housing as described in any one of claims 1 to 8; an electromagnetic wave generating unit that generates electromagnetic waves; and an electromagnetic wave radiating unit that is housed inside the conductive housing and radiates electromagnetic waves from the electromagnetic wave generating unit into the space inside the conductive housing.

10. An electromagnetic wave heating device as described in claim 9, wherein the electrical connections between the first shield and the conductive mesh in the second shield are connected at intervals of less than 1 / 10 of the wavelength of the electromagnetic waves generated by the electromagnetic wave generating unit.

11. A sensor device comprising: a conductive housing as claimed in any one of claims 1 to 8; and a sensor element disposed inside the space of the conductive housing and configured to acquire information from outside the space of the conductive housing via a conductive mesh in the conductive housing.

12. The sensor device according to claim 11, wherein the sensor element is a visible light camera.

13. The sensor device according to claim 11, wherein the sensor element is an infrared camera.

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