electronic equipment

Abstract

To vary a resonance frequency of a housing from a frequency of electromagnetic noise from a noise generation source, in an electronic device which has a housing for housing the noise generation source.SOLUTION: A housing of an electronic device 10 comprises: first and second housing components 16, 18; a dielectric 26; and a conductive fixing screw 24. The first housing component 16 has a lateral wall 16b including a first fixing part 16d. The second housing component 18 has a lateral wall 18b including a second fixing part 18c. Top surfaces of the lateral walls 16b, 18b of the first and second housing components 16, 18 face each other. The first and second fixing parts 16d, 18c come into contact with each other via the dielectric 26. The fixing screw 24 passes through a through-hole 16e formed on one of the first fixing part 16d and the second fixing part 18c, and then penetrates the dielectric 26 so as to be screwed into a female screw hole 18d formed on the other one of the first and second fixing parts.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to electronic devices. [Background technology]

[0002] For example, Patent Document 1 discloses an electronic device having a circuit board and a metal housing with an accommodation space for accommodating the circuit board. The housing includes a housing main body with an opening for accommodating the circuit board, and a lid that closes the opening of the housing main body. An annular protrusion that protrudes toward the housing main body is formed on the outer peripheral edge of the lid. An annular press-fit groove into which the protrusion of the lid is press-fit is formed on the edge of the opening of the housing main body. Press-fitting the protrusion of the lid into the press-fit groove of the housing main body closes the accommodation space, suppressing electromagnetic noise radiation (EMI) from the printed circuit board to the outside of the case and improving the resistance of the printed circuit board to malfunction due to external electromagnetic noise (EMS). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Actual proposal No. 6-26295 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, the housing of the electronic device described in Patent Document 1 may resonate due to electromagnetic noise generated from the printed circuit board. If the resonant frequency of the housing substantially matches the frequency of the electromagnetic noise, the electromagnetic noise may be amplified by the resonance. As a result, the electronic device may radiate electromagnetic noise to the outside.

[0005] Therefore, an object of the present disclosure is to make the resonant frequency of an electronic device having a noise source that generates electromagnetic noise and a housing that accommodates the noise source different from the frequency of the electromagnetic noise generated by the noise source. [Means for solving the problem]

[0006] In order to solve the above problem, according to one aspect of the present disclosure, a noise source that generates electromagnetic noise; a housing made of a conductive material and containing the noise generating source; the housing includes first and second housing parts defining an accommodation space for accommodating the noise generation source, a dielectric material disposed between the first and second housing parts, and a conductive fixing screw for fixing the first and second housing parts together; the first housing part includes a first fixing portion fixed to the second housing part and has a side wall protruding toward the second housing part; the second housing part includes a second fixing portion fixed to the first housing part and has a side wall protruding toward the first housing part; a top surface of the side wall of the first housing part and a top surface of the side wall of the second housing part face each other; a through hole is formed in one of the first fixing portion of the first housing part and the second fixing portion of the second housing part, and an internally threaded hole is formed in the other of the first fixing portion of the first housing part and the second fixing portion of the second housing part; the first fixed portion and the second fixed portion are in contact with each other via the dielectric, An electronic device is provided, wherein the fixing screw passes through the through hole, penetrates the dielectric, and threads into the female threaded hole. [Effects of the Invention]

[0007] According to the present disclosure, in an electronic device having a noise source that generates electromagnetic noise and a housing that accommodates the noise source, the resonant frequency of the housing can be made different from the frequency of the electromagnetic noise generated by the noise source. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a top perspective view of an electronic device according to a first embodiment of the present disclosure; [Figure 2] Exploded perspective view of electronic device [Figure 3] 1 is a bottom perspective view of a first housing part; [Figure 4] Cross-section of the electronic device along line AA in Figure 1 [Figure 5] Cross-section of the electronic device along line BB in Figure 1 [Figure 6] FIG. 10 is a bottom perspective view of a first housing component in the electronic device of the comparative example; [Figure 7] FIG. 10 is a top perspective view of a second housing component in the electronic device of the comparative example; [Figure 8] Cross-sectional view of an electronic device of a comparative example [Figure 9] 1 is a top view showing the electric field distribution in an electronic device of a comparative example; [Figure 10] Frequency-EMI characteristic diagram showing the shift in the housing's resonant frequency [Figure 11] 10 is a top perspective view of an electronic device according to a second embodiment of the present disclosure; [Figure 12] Exploded perspective view of electronic device [Figure 13] 1 is a bottom perspective view of a first housing part; [Figure 14] Cross-sectional view of the electronic device taken along line CC in Figure 11 [Figure 15] Cross-section of the electronic device along line DD in Figure 11 [Figure 16] Frequency-EMI plot showing another shift in the housing's resonant frequency [Figure 17] Frequency-EMI plot showing yet another shift in the housing's resonant frequency [Figure 18]FIG. 10 is a bottom perspective view of a first housing component of an electronic device according to another embodiment of the present disclosure. [Figure 19] Frequency-EMI plot showing further shifts in the housing's resonant frequency DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of well-known matters or redundant explanation of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art.

[0010] The inventors have provided the accompanying drawings and the following description to enable those skilled in the art to fully understand the present disclosure, and do not intend for them to limit the subject matter described in the claims.

[0011] (Embodiment 1) Fig. 1 is a top perspective view of an electronic device according to a first embodiment of the present disclosure. Fig. 2 is an exploded perspective view of the electronic device. Note that the XYZ Cartesian coordinate system shown in the figure is intended to facilitate understanding of the embodiment of the present disclosure and is not intended to limit the embodiment of the present disclosure.

[0012] 1 and 2 , electronic device 10 according to a first embodiment of the present disclosure is, for example, a compact camera mounted on a vehicle. Electronic device 10 includes circuit board 12, which is a source of electromagnetic noise, and housing 14, which is made of a conductive material such as a metal material and houses circuit board 12. Housing 14 has a rectangular parallelepiped shape and includes first housing component 16 and second housing component 18.

[0013] Fig. 3 is a bottom perspective view of the first housing part, Fig. 4 is a cross-sectional view of the electronic device taken along line AA in Fig. 1, and Fig. 5 is a cross-sectional view of the electronic device taken along line BB in Fig. 1.

[0014] 4 and 5, the first housing component 16 and the second housing component 18 engage with each other to define an accommodation space R that accommodates the circuit board 12. Specifically, in the first embodiment, the first housing component 16 is generally cylindrical with a bottom and includes a rectangular plate-shaped base portion 16a and a sidewall 16b that protrudes from the outer periphery of the base portion 16a toward the second housing component 18. The second housing component 18 is generally cylindrical with a bottom and includes a rectangular plate-shaped base portion 18a and a sidewall 18b that protrudes from the outer periphery of the base portion 18b toward the first housing component 16. The sidewall 16b of the first housing component 16 and the sidewall 18b of the second housing component 18 face each other at their respective top surfaces. When the first housing part 16 and the second housing part 18 engage with each other, an accommodation space R is defined which is surrounded by the base portion 16a and side wall 16b of the first housing part 16 and the base portion 18a and side wall 18b of the second housing part 18.

[0015] In the first embodiment, the circuit board 12 is fixed to the base portion 18a of the second housing component 18 via a plurality of fixing screws 20. This electrically connects the circuit board 12 to the second housing component 18 as a ground (the potential of the second housing component 18 is the same as the ground potential of the circuit board 12). If the electronic device 10 is a compact camera, optical elements such as a lens are attached to the second housing component 18. A connection cable 22 (including a power cable and a signal cable) that connects the circuit board 12 to an external device (not shown) passes through a through-hole 16c formed in the base portion 16a of the first housing component 16.

[0016] The first and second housing components 16, 18 are made of a conductive material such as a metal material. In the first embodiment, the first and second housing components 16, 18 are made of aluminum die-cast (ADC12). This suppresses the radiation of electromagnetic noise generated from the circuit board 12 to the outside of the electronic device 10 (EMI: Electromagnetic Interference), and improves the resistance of the circuit board 12 to malfunction due to external electromagnetic noise (EMS: Electromagnetic Susceptibility).

[0017] In the first embodiment, the first and second housing parts 16, 18 are fixed to each other via a plurality of fixing screws 24.

[0018] Specifically, the side wall 16b of the first housing component 16 includes a first fastening portion 16d that is fastened to the second housing component 18. Also, the side wall 18b of the second housing component 18 includes a second fastening portion 18c that is fastened to the first fastening portion 16d of the first housing component 16.

[0019] In the first embodiment, two first fixing portions 16d are arranged diagonally on the rectangular side wall 16b of the first housing component 16 when viewed in the engagement direction (viewed in the Z-axis direction) of the first and second housing components 16, 18. Similarly, two second fixing portions 18c are arranged diagonally on the rectangular side wall 18b of the second housing component 18.

[0020] In the first embodiment, the first fixing portion 16d of the first housing component 16 has a through hole 16e formed therein, through which the fixing screw 24 passes. The second fixing portion 18c of the second housing component 18 has an internally threaded hole 18d formed therein, into which the fixing screw 24 threads. The fixing screw 24 passes through the through hole 16e of the first fixing portion 16d and threads into the internally threaded hole 18d of the second fixing portion 18c, thereby fixing the first fixing portion 16d and the second fixing portion 18c to each other and connecting them in a DC manner. Alternatively, an internally threaded hole may be formed in the first fixing portion 16d, and a through hole may be formed in the second fixing portion 18c.

[0021] In the first embodiment, the first housing component 16 and the second housing component 18 are made of die-cast aluminum and anodized. Therefore, the contact surfaces of the first fixing portion 16d and the second fixing portion 18c are covered with an oxide film and are not connected in a direct current manner. However, the first fixing portion 16d and the second fixing portion 18c are connected in a direct current manner via a fixing screw 24 made of a conductive material such as a metal material. That is, the head 24a of the fixing screw 24 contacts the first fixing portion 16d and is connected in a direct current manner, and the shank 24b of the fixing screw 24, which has an external thread, is threaded into the female threaded hole 18d of the second fixing portion 18c and is connected in a direct current manner. The oxide film on the portion of the first fixing portion 16d that contacts the head 24a of the fixing screw 24 is scraped off by the rotation of the head 24a when the fixing screw 24 is tightened, so that the portion can be connected in a direct current manner to the head 24a of the fixing screw 24. Furthermore, the female screw hole 18d is formed by tapping after anodizing, so that it can be connected to the shaft portion 24b of the fixing screw 24 in a direct current manner.

[0022] In the first embodiment, the side wall 16b of the first housing component 16 includes first inner wall portions 16f that protrude toward the second housing component 18 and extend in a direction (X-axis direction or Y-axis direction) away from each of the multiple first fixing portions 16d. Specifically, two first inner wall portions 16f extend in a direction away from one first fixing portion 16d. In the first embodiment, the multiple (four) first inner wall portions 16f are connected to each other to form a single annular inner wall portion.

[0023] In the first embodiment, the side wall 18b of the second housing component 18 includes a plurality of second inner wall portions 18e that protrude toward the first housing component 16 and extend in a direction (X-axis direction or Y-axis direction) away from the plurality of second fixing portions 18c. Specifically, two second inner wall portions 18e extend in a direction away from one first fixing portion 18c. In the first embodiment, the plurality of (four) second inner wall portions 18e are connected to each other to form a single annular inner wall portion. The second inner wall portions 18e are arranged side by side on the outside of the first inner wall portion 16f of the first housing component 16 with a gap therebetween. Note that if the surfaces of the first and second housing components 16, 18 are covered with an oxide film (insulating layer), the second inner wall portions 18e may be in contact with the first inner wall portion 16f.

[0024] Furthermore, in the first embodiment, the first fixing portion 16d of the first housing component 16 and the second fixing portion 18c of the second housing component 18 are not in direct contact with each other, but are in contact with each other via a dielectric 26. The dielectric 26 is a member made of, for example, a resin material, and has a through hole 26a through which the shank 24b of the fixing screw 24 passes. The presence of such a dielectric 26 makes it possible to make the resonant frequency of the housing 14 different from the frequency of electromagnetic noise. This will be explained with reference to a comparative example.

[0025] Fig. 6 is a bottom perspective view of a first housing part in the electronic device of the comparative example. Fig. 7 is a top perspective view of a second housing part in the electronic device of the comparative example. Fig. 8 is a cross-sectional view of the electronic device of the comparative example. Fig. 9 is a top view showing the electric field distribution in the electronic device of the comparative example. Fig. 10 is a frequency-EMI characteristic diagram showing the shift in the resonant frequency of the housing.

[0026] 6 to 9, in the electronic device 110 of the comparative example, the first housing component 116 includes a rectangular plate-shaped base portion 116a and a sidewall 116b that protrudes from the outer periphery of the base portion 116a toward the second housing component 118. The second housing component 118 includes a rectangular plate-shaped base portion 118a and a sidewall 118b that protrudes from the outer periphery of the base portion 118a toward the first housing component 116. The sidewall 116b of the first housing component 116 and the sidewall 118b of the second housing component 118 face each other at their respective top surfaces. When the first housing component 116 and the second housing component 118 are engaged with each other, an accommodation space R that accommodates the circuit board 12 is defined by the base portion 116a and sidewall 116b of the first housing component 116 and the base portion 118a and sidewall 118b of the second housing component 118.

[0027] Furthermore, in electronic device 110 of the comparative example, side wall 116b of first housing component 116 includes first fixing portion 116d that is fixed to second housing component 118. Furthermore, side wall 118b of second housing component 118 includes second fixing portion 118c that is fixed to first fixing portion 116d of first housing component 116. First fixing portion 116d and second fixing portion 118c are fixed to each other via fixing screws 24.

[0028] In the electronic device 110 of the comparative example, unlike the electronic device 10 of the present embodiment 1, the first fixing portion 116d on the side wall 116a of the first housing component 116 and the second fixing portion 118c on the side wall 118a of the second housing component 118 do not sandwich a dielectric but are in direct contact with each other.

[0029] Furthermore, in electronic device 110 of the comparative example, two first fixing portions 116d are arranged diagonally on rectangular side wall 116b of first housing component 116 when viewed in the engagement direction (viewed in the Z-axis direction) of first and second housing components 116, 118. Similarly, two second fixing portions 118c are arranged diagonally on rectangular side wall 118b of second housing component 118.

[0030] In the electronic device 110 of the comparative example, a plurality of first inner wall portions 116f are provided on the side wall 116b of the first housing component 116 other than the first fixed portion 116d, i.e., the portion not fixed to the second housing component 118. The first inner wall portions 116f protrude toward the second housing component 116 and extend in a direction (X-axis direction or Y-axis direction) away from the plurality of first fixed portions 116d. Specifically, two first inner wall portions 116f extend in a direction away from one first fixed portion 116d. The plurality (four) of first inner wall portions 116f are connected to each other to form a single annular inner wall portion.

[0031] Furthermore, in the electronic device 110 of the comparative example, a portion of the side wall 118b of the second housing component 118 other than the second fixed portion 118c, i.e., a portion not fixed to the first housing 116, is provided with a plurality of second inner wall portions 118e that protrude toward the first housing component 116 and extend in a direction (X-axis direction or Y-axis direction) away from the plurality of second fixed portions 118c. Specifically, two second inner wall portions 118e extend in a direction away from one first fixed portion 118c. The plurality (four) second inner wall portions 118e are connected to each other to form a single annular inner wall portion. The second inner wall portions 118e are arranged side by side on the outside of the first inner wall portion 116f of the first housing component 116 with a gap therebetween. If the surfaces of the first and second housing components 16, 18 are covered with an oxide film (insulating layer), the second inner wall portion 18e may be in contact with the first inner wall portion 16f.

[0032] In the electronic device 110 of this comparative example, the housing 114 may resonate due to electromagnetic noise generated from the circuit board 12 therein. Specifically, as shown in FIG. 9, an electric field (cross-hatched portion) with a higher intensity than other portions is generated between the side wall 116b of the first housing component 116 and the side wall 118b of the second housing component 118. The electric field intensity increases with increasing distance from the first fixing portion 116d (second fixing portion 118c). In other words, the electric field intensity is highest at the corner of the side wall 116b (118b) where the first fixing portion 116d (second fixing portion 118c) is not provided.

[0033] When this electric field distribution occurs, the portions of the first and second housing components 116 and 118 where the electric field intensity is high function as a dipole antenna. Specifically, the first fixed portion 116d and the second fixed portion 118c, which are fixed to each other via the fixing screws 24, function as a feed point of the dipole antenna. Furthermore, the two first inner wall portions 116f extending away from the first fixed portion 116d, which functions as the feed point, and the two second inner wall portions 118e extending away from the second fixed portion 118c function as elements of the dipole antenna that receive electromagnetic noise. When this dipole antenna receives electromagnetic noise generated by the circuit board 12, the housing 114 resonates.

[0034] 9, when viewed in the engagement direction of the first housing component 116 and the second housing component 118 (when viewed in the Z-axis direction), if one side of the rectangular housing 114 (i.e., side wall 114b) has a length that is substantially ¼ of the wavelength λ of the frequency of the electromagnetic noise, the housing 114 resonates strongly. That is, when the extension lengths of the two first inner wall portions 116f extending in the direction away from the first fixing portion 116d (X-axis or Y-axis direction) and the two second inner wall portions 118e extending in the direction away from the second fixing portion 118c (X-axis or Y-axis direction) are ¼ of the wavelength λ of the frequency of the electromagnetic noise, the housing 114 has a resonant frequency that is substantially the same as the frequency of the electromagnetic noise. In other words, the housing 114 is provided with a "half-wavelength dipole antenna."

[0035] In order to suppress such housing resonance, in the electrical device 10 according to the first embodiment, the first fixing portion 16d on the side wall 16b of the first housing part 16 and the second fixing portion 18c on the side wall 18b of the second housing part 18 are in contact with each other via a dielectric 26.

[0036] The frequency-EMI characteristic diagram in Fig. 10 is a result obtained by simulation, and shows the intensity of electromagnetic noise (EMI) radiated from the housing as a result of changing the frequency of electromagnetic noise radiated from circuit board 12. In Fig. 10, the solid line indicates the intensity of electromagnetic noise radiated from housing 114 of electronic device 110 of the comparative example. The dashed line indicates the intensity of electromagnetic noise radiated from housing 14 of electronic device 10 according to the first embodiment, when height h of dielectric 26 (i.e., the distance between first fixing portion 16d and second fixing portion 18c) is 2.5 mm. The dashed line indicates the intensity of electromagnetic noise radiated from housing 14 of electronic device 10 according to the first embodiment, when height h of dielectric 26 is 4.5 mm.

[0037] 10, in the housing 14 of the electronic device 10 according to the first embodiment, as the height h of the dielectric 26 increases, the peak value of the intensity of the EMI radiated from the housing 14 shifts to a lower frequency, i.e., the resonant frequency of the housing 14 shifts to a lower frequency. At the same time, the peak value also decreases. Furthermore, compared to the peak value of the intensity of the EMI radiated from the housing 114 of the electronic device 110 of the comparative example, which does not include the dielectric 26, the peak value in the first embodiment shifts to a lower frequency and decreases.

[0038] This shift in the peak value of the EMI intensity is believed to be caused by the shank 24b of the fixing screw 24, which penetrates the dielectric 26, functioning as an "inductance." Specifically, the first fixing portion 16d of the first housing component 16 and the second fixing portion 18c of the second housing component 18 are electrically connected via an "inductance." When the first housing component 16 and the second housing component 18 are electrically connected via an "inductance," the length of the "element" of the "dipole antenna" formed by this connection increases. As a result, the peak value of the EMI intensity radiated from the housing 14 shifts to a lower frequency, i.e., the resonant frequency of the housing shifts to a lower frequency. The inventors discovered this frequency characteristic with respect to the inductance between the first and second housing components 16 and 18 through simulations.

[0039] Furthermore, providing the dielectric 26 has the advantage that not only does it shift the peak value of the intensity of the EMI radiated from the housing 14 to the lower frequency side, but it also reduces the intensity of the EMI radiated from the housing 14. This is because the radiation efficiency of electromagnetic waves decreases at the point where the first fixed portion 16d or the fixed portion 18c contacts the dielectric.

[0040] Therefore, by bringing the first fixing portion 16d of the first housing component 16 and the second fixing portion 18c of the second housing component 18 into contact with each other via a dielectric 26 of an appropriate height h, the resonant frequency of the housing 14 can be made different from the frequency of the electromagnetic noise generated from the circuit board 12.

[0041] Furthermore, as in the comparative electronic device 110 shown in Figure 9, even if one side of the rectangular housing 14 in the electronic device 10 of this embodiment 1 (i.e., the length in the extension direction of the side walls 16b, 18b) is substantially 1 / 4 the wavelength λ of the frequency of the electromagnetic noise when viewed in the engagement direction of the first housing part 16 and the second housing part 18 (viewed in the Z-axis direction), the resonant frequency of the housing 14 can be made different from the frequency of the electromagnetic noise generated from the circuit board 12 without changing the size of the housing 14.

[0042] According to the first embodiment, in an electronic device having a circuit board that generates electromagnetic noise and a housing that accommodates the circuit board, the resonant frequency of the housing can be made different from the frequency of the electromagnetic noise generated from the circuit board.

[0043] (Embodiment 2) The present embodiment 2 is an improved version of the embodiment 1. Therefore, the following description will focus on the differences between the embodiment 2 and the embodiment 1.

[0044] Fig. 11 is a top perspective view of an electronic device according to a second embodiment of the present disclosure. Fig. 12 is an exploded perspective view of the electronic device. Fig. 13 is a bottom perspective view of a first housing component. Fig. 14 is a cross-sectional view of the electronic device taken along line CC in Fig. 11. Fig. 15 is a cross-sectional view of the electronic device taken along line DD in Fig. 11.

[0045] 11 and 12 , electronic device 210 according to the second embodiment of the present disclosure includes circuit board 212, which is a source of electromagnetic noise, and housing 214, which is made of a conductive material such as a metal material and which houses circuit board 212. Housing 214 has a rectangular parallelepiped shape and includes first housing component 216 and second housing component 218.

[0046] In the second embodiment, first housing component 216 is generally cylindrical with a bottom, and includes a rectangular plate-shaped base portion 216a and a sidewall 216b protruding from the outer periphery of base portion 216a toward second housing component 218. Second housing component 218 is generally cylindrical with a bottom, and includes a rectangular plate-shaped base portion 218a and a sidewall 218b protruding from the outer periphery of base portion 218a toward first housing component 216. Circuit board 212 is fixed to base portion 218a of second housing component 218 via a plurality of fixing screws 220.

[0047] In the second embodiment, the first and second housing components 216, 218 are fixed to each other via a plurality of fixing screws 224. Specifically, the side wall 216b of the first housing component 216 includes a first fixing portion 216d that is fixed to the second housing component 218. Furthermore, the side wall 218b of the second housing component 218 includes a second fixing portion 218c that is fixed to the first fixing portion 218d of the first housing component 216.

[0048] A portion of the side wall 216b of the first housing component 216 other than the first fastening portion 216d is not fixed to the second housing component 218. Similarly, a portion of the side wall 218b of the second housing component 218 other than the second fastening portion 218 is not fixed to the first housing component 216.

[0049] In the second embodiment, the side wall 216b of the first housing component 216 includes a plurality of protrusions 216f that protrude toward the second housing component 218 and extend in a direction (X-axis direction or Y-axis direction) away from each of the plurality of first fixing portions 216d. Specifically, two protrusions 216f extend in a direction away from one first fixing portion 216d.

[0050] Furthermore, in the second embodiment, the side wall 218b of the second housing component 218 extends in a direction (X-axis direction or Y-axis direction) away from the second fixing portion 218c and includes a plurality of grooves 218e into which the plurality of protrusions 216f of the first housing component 216 enter. Specifically, two grooves 218e extend away from one second fixing portion 218c.

[0051] Furthermore, in the case of this embodiment 2, a notch portion 216g is formed on the top surface of at least one of the multiple protrusion portions 216f of the side wall 216b of the first housing part 216, and in the case of this embodiment 2, a notch portion 16g is formed on each of the multiple protrusion portions 216f.

[0052] Notch 216g is a groove extending from the inside to the outside of housing 214, and divides the top surface of protrusion 216f. In the second embodiment, notch 216b is formed in the center of protrusion 216f in the extending direction (X-axis direction or Y-axis direction).

[0053] Furthermore, in the case of the second embodiment, first fixing portion 216d of first housing component 216 and second fixing portion 218c of second housing component 218 are not in direct contact with each other, but are in contact with each other via dielectric 226. Dielectric 226 is a member made of, for example, a resin material, and has through-hole 226a through which shank 224b of fixing screw 224 passes.

[0054] By appropriately setting the protrusion amount p of the protrusion portion 216f on the side wall 216b of the first housing component 216, the width w of the cutout portion 216g, the depth d of the groove 218e on the side wall 218b of the second housing component 218, and the height h of the dielectric 226, the resonant frequency of the housing 214 can be shifted, thereby making it different from the frequency of the electromagnetic noise generated from the circuit board 212.

[0055] Specifically, first, in order to achieve the first resonant frequency shift, the protrusion amount p of the protrusion portion 216f on the side wall 216b of the first housing component 216 and the depth d of the groove 218e on the side wall 218b of the second housing component 218 are appropriately set.

[0056] Furthermore, in order to achieve another shift in the resonant frequency, the width w of the notch 216g in the protrusion 216f of the side wall 216b of the first housing part 216 is appropriately set.

[0057] Then, in order to achieve yet another shift in the resonant frequency, the height h of the dielectric 226 between the first fixed portion 216d of the first housing part 216 and the second fixed portion 218c of the second housing part 218 is appropriately set.

[0058] By realizing a combination of these three resonant frequency shifts, the resonant frequency of housing 214 can be made different from the frequency of the electromagnetic noise generated from circuit board 212.

[0059] First, the shift in the resonant frequency of the housing 214 due to the protrusion amount p of the protrusion 216f on the side wall 216b of the first housing component 216 and the depth d of the groove 218e on the side wall 218b of the second housing component 218 will be described.

[0060] FIG. 16 is a frequency-EMI characteristic diagram showing another shift in the resonant frequency of the housing.

[0061] The frequency-EMI characteristic diagram in FIG. 16 is a result obtained by simulation, and shows the intensity of electromagnetic noise (EMI) radiated from the housing as the frequency of electromagnetic noise radiated from the circuit board is changed. In FIG. 16, the solid line indicates the intensity of electromagnetic noise radiated from housing 114 of electronic device 110 of the comparative example. The dashed line indicates the intensity of electromagnetic noise radiated from electronic device 210 according to the second embodiment, in which cutout portion 216g and dielectric 226 have been removed, when depth d of groove 218e in sidewall 218b of second housing component 218 is 2 mm. The dashed-dotted line indicates the intensity of electromagnetic noise radiated from housing 214 of electronic device 210 according to the second embodiment, in which cutout portion 216g and dielectric 226 have been removed, when depth d of groove 218e is 3 mm.

[0062] 16, in housing 214 of electronic device 210 according to the second embodiment, from which cutout 216g and dielectric 226 have been removed, when depth d of groove 218e of second housing component 218 increases, the peak value of the intensity of EMI radiated from housing 214 shifts to a lower frequency, i.e., the resonant frequency of housing 214 shifts to a lower frequency. Furthermore, the peak value of the intensity of EMI radiated from housing 214 is lower than the peak value in electronic device 110 of the comparative example.

[0063] As shown in FIGS. 8 and 14 , this shift in the peak value of EMI intensity is caused by differences in the surface areas S1, S2, S3, and S4 (enlarged and indicated by bold lines) of the portions of the first and second housing components that face each other through an insulator in the region where they engage with each other. The term "insulator" here refers to air, an oxide film, a sealing material, and the like. That is, when comparing electronic device 210 according to the second embodiment with electronic device 110 of the comparative example, as shown in FIGS. 8 and 14 , the surface areas S1 and S2 of the portions of the electronic device 210 according to the second embodiment that face each other at close range are larger than the surface areas S3 and S4 of the portions of the electronic device 110 of the comparative example. Furthermore, the greater the depth d of groove 218e in sidewall 218b of second housing component 218, the larger the surface area of the portions of the portions of the electronic device 210 that face each other at close range. The larger the surface area, the greater the capacitive coupling between the first and second housing components, which reduces the overall strength of the electric field generated between the first and second housing components. As a result, the peak value of the EMI intensity radiated from the housing 214 shifts to a lower frequency, i.e., the resonant frequency of the housing shifts to a lower frequency. The inventors found these frequency characteristics with respect to the surface areas of the first and second housing components 216, 218 through simulations.

[0064] Therefore, by appropriately setting the protrusion amount p of the protrusion portion 216f of the first housing component 216 and the depth d (size in the Z-axis direction) of the groove 218e of the second housing component 218, that is, by appropriately setting the surface area of the portions that face each other at close range, the resonant frequency of the housing 214 can be made different from the frequency of the electromagnetic noise generated from the circuit board 212.

[0065] Next, a shift in the resonant frequency of the housing 214 due to the width w of the notch 216g in the protruding portion 216f of the cylindrical portion 216b of the first housing component 216 will be described.

[0066] FIG. 17 is a frequency-EMI characteristic diagram showing yet another shift in the resonant frequency of the housing.

[0067] The frequency-EMI characteristic diagram in Figure 17 is a result obtained by simulation, and shows the intensity of electromagnetic noise (EMI) radiated from the housing as the frequency of electromagnetic noise radiated from the circuit board is changed. In Figure 17, the solid line shows the intensity of electromagnetic noise radiated from the housing 114 of the comparative electronic device 110. The dashed line shows the intensity of electromagnetic noise radiated from the housing 114 of the comparative electronic device 110, which has a cutout formed in the center of the first inner wall portion 116f of the first housing component 116, when the width w (the size in the extension direction of the inner wall portion 116f) is 3 mm. The dashed line shows the intensity of electromagnetic noise radiated from the housing 114 of the comparative electronic device 110, which has a cutout formed in the center, when the width w of the cutout is 5 mm.

[0068] 17, in housing 114 of electronic device 110 of the comparative example, in which a cutout is formed, when width w of the cutout formed in first inner wall portion 118f of first housing component 116 increases, the peak value of the intensity of EMI radiated from housing 114 shifts to a lower frequency, i.e., the resonant frequency of housing 114 shifts to a lower frequency. Furthermore, compared to the peak value of the intensity of EMI radiated from housing 114 of electronic device 110 of the comparative example in which a cutout is not formed, the peak value shifts to a lower frequency.

[0069] It is believed that this shift in the peak value of EMI intensity is caused by a change in the length of the "element" of the "dipole antenna" due to the cutout. In the second embodiment, as shown in FIG. 13, the overall length of the portion (shown cross-hatched) facing the second housing component 218 via the insulator is increased by the length of the rising portion 216h and the falling portion 216i of the cutout 216g. This increases the length functioning as an "element" of the "dipole antenna." As a result, the peak value of the intensity of EMI radiated from the housing 114 shifts to a lower frequency, i.e., the resonant frequency of the housing 114 shifts to a lower frequency. The inventors discovered this change in the frequency characteristics of the housing 114 due to the cutout through simulations.

[0070] Furthermore, providing a cutout as in the second embodiment has the advantage that not only does it shift the peak value of the intensity of EMI radiated from housing 214 to the lower frequency side, but it also has the potential to reduce the intensity of EMI radiated from housing 214. This is because it is expected that the radiation efficiency of electromagnetic waves will decrease at the corners of the cutout.

[0071] 17 shows the shift in resonant frequency when a cutout portion is formed in the electronic device 110 of the comparative example shown in FIGS. 6 to 9. It is presumed that a similar shift in resonant frequency occurs when a cutout portion 216g is provided in the protrusion portion 216f of the tubular portion 216b of the first housing component 216, as in the second embodiment.

[0072] Therefore, by providing a notch 216g of an appropriate width w in the center of the extension direction of the protrusion 116f on the side wall 216b of the first housing component 216, the resonant frequency of the housing 214 can be made different from the frequency of the electromagnetic noise generated from the circuit board 212.

[0073] Next, the shift in the resonant frequency of the housing 214 due to the height h of the dielectric 226 between the first fixing portion 216d of the first housing part 216 and the second fixing portion 218c of the second housing part 218 is as explained in the above-mentioned embodiment 1 with reference to FIG. 10.

[0074] In this second embodiment, as in the above-described embodiments, in an electronic device having a circuit board that generates electromagnetic noise and a housing that accommodates the circuit board, the resonant frequency of the housing can be made different from the frequency of the electromagnetic noise generated from the circuit board.

[0075] Although the present disclosure has been described above with reference to the first and second embodiments, the present disclosure is not limited to these embodiments.

[0076] For example, in the above-described first and second embodiments, the noise source housed within the housing 14 that generates electromagnetic noise that may cause the housing 14 to resonate is the circuit board 12. However, in the embodiments of the present disclosure, the noise source is not limited to the circuit board. The noise source may also be, for example, a sensor.

[0077] In the first embodiment described above, the dielectric 26 disposed between the first fixing portion 16d of the first housing component 16 and the second fixing portion 18c of the second housing component 18 is made of a resin material. However, the embodiments of the present disclosure are not limited to this. The dielectric may be, for example, air. In this case, the first fixing portion 16d and the second fixing portion 18c face each other with a gap between them. Furthermore, dispersing metal particles inside the dielectric reduces the electromagnetic wave radiation efficiency, which has the advantage of further reducing the intensity of EMI radiated from the housing 14.

[0078] Furthermore, in the case of the above-described second embodiment, the notch 216g is disposed in the center in the extension direction of the protrusion 216f in the side wall 216b of the first housing component 216. However, the position on the protrusion where the notch is disposed is not limited to the center.

[0079] Fig. 18 is a bottom perspective view of a first housing component of an electronic device according to another embodiment of the present disclosure, and Fig. 19 is a frequency-EMI characteristic diagram illustrating yet another shift in the resonant frequency of the housing.

[0080] 18 shows a first housing component 316 in an electronic device according to another embodiment. The electronic device according to this embodiment corresponds to the electronic device 110 of the comparative example shown in FIGS. 6 to 9, with a cutout 316g formed therein. The cutout 316g is formed in the first inner wall portion 316f of the side wall portion 316b of the first housing component 316, not in the center in the extension direction thereof, but at a position offset from the center. Specifically, the cutout 316g is formed near a corner formed by the connection of two first inner wall portions 316f.

[0081] When a notch 316g is formed in the first inner wall portion 316f near the corner in this manner, as shown in Figure 19, the peak value (dashed double-dashed line) of the intensity of the EMI radiated from the housing shifts to the higher frequency side compared to the peak value (solid line) of the comparative electronic device 110 in which no notch is formed.

[0082] This shift in the peak value of EMI intensity is thought to be caused by the change in the length of the "dipole antenna" element due to the cutout. As mentioned above, when a cutout is formed away from a corner, the total length of the opposing portion, separated by an insulator, increases by the length of the rising and falling portions of the cutout. In contrast, when a cutout is formed near a corner, the cutout is located far from the first and second fixed portions, which are the power feed points of the "dipole antenna." The presence of a cutout far from the power feed points reduces the function of the "element" at that location. This reduction in function is greater than the effect of the increase in the total length of the opposing portion, separated by an insulator, due to the length of the rising and falling portions of the cutout. Therefore, when a cutout is formed near a corner, the length of the "element" shortens. As a result, when a cutout is formed near a corner, the peak value of the EMI intensity radiated from the housing shifts to a higher frequency.

[0083] Therefore, in the second embodiment described above, even if the cutout portion 216g is located near a corner of the housing, the resonant frequency of the housing can be made different from the frequency of the electromagnetic noise generated from the circuit board.

[0084] That is, an electronic device according to one embodiment of the present disclosure, in a broad sense, comprises a noise generation source that generates electromagnetic noise, and a housing made of a conductive material and accommodating the noise generation source, wherein the housing comprises first and second housing parts that define an accommodating space that accommodates the noise generation source, a dielectric disposed between the first and second housing parts, and a conductive fixing screw that fixes the first and second housing parts, wherein the first housing part includes a first fixing portion that is fixed to the second housing part and has a side wall that protrudes toward the second housing part, The second housing component includes a second fixing portion fixed to the first housing component and has a side wall protruding toward the first housing component, the top surface of the side wall of the first housing component and the top surface of the side wall of the second housing component face each other, a through hole is formed in one of the first fixing portion of the first housing component and the second fixing portion of the second housing component, and an internally threaded hole is formed in the other, the first fixing portion and the second fixing portion contact each other via the dielectric, and the fixing screw passes through the through hole, penetrates the dielectric, and screws into the internally threaded hole.

[0085] As described above, the embodiments have been described as examples of the technology of the present disclosure. For this purpose, the accompanying drawings and detailed description have been provided. Therefore, the components described in the accompanying drawings and detailed description may include not only components essential for solving the problem, but also components that are not essential for solving the problem in order to exemplify the technology. Therefore, the fact that these non-essential components are described in the accompanying drawings or detailed description should not be interpreted as immediately indicating that these non-essential components are essential.

[0086] Furthermore, since the above-described embodiments are intended to illustrate the technology of the present disclosure, various modifications, substitutions, additions, omissions, etc. can be made within the scope of the claims or their equivalents. [Industrial Applicability]

[0087] The present disclosure is applicable to electronic devices that have a noise source that generates electromagnetic noise and a housing that accommodates the noise source. [Explanation of symbols]

[0088] 10 Electronic equipment 16 First housing part 16b side wall 16d First fixing part 16e through hole 18 Second housing part 18b side wall 18c Second fixing part 18d female thread hole 24 Fixing screw 26 Dielectrics

Claims

1. a noise source that generates electromagnetic noise; a housing made of a conductive material and containing the noise generating source; the housing includes first and second housing parts defining an accommodation space for accommodating the noise generation source, a dielectric disposed between the first and second housing parts, and a conductive fixing screw for fixing the first and second housing parts together; the first housing part includes a first fixing portion fixed to the second housing part and has a side wall protruding toward the second housing part; the second housing part includes a second fixing portion fixed to the first housing part and has a side wall protruding toward the first housing part; a top surface of the side wall of the first housing part and a top surface of the side wall of the second housing part face each other; a through hole is formed in one of the first fixing portion of the first housing part and the second fixing portion of the second housing part, and an internally threaded hole is formed in the other of the first fixing portion of the first housing part and the second fixing portion of the second housing part; the first fixed portion and the second fixed portion are in contact with each other via the dielectric, The electronic device, wherein the fixing screw passes through the through hole, penetrates the dielectric, and is screwed into the female threaded hole.

2. The electronic device according to claim 1 , wherein the length of the side wall of the first housing part or the side wall of the second housing part in the extending direction is ¼ of the wavelength of the frequency of the electromagnetic noise.

3. two first fixing portions are arranged diagonally on the first housing part, The electronic device according to claim 1 , wherein two of the second fixing portions are arranged diagonally on the second housing part.

4. The electronic device according to claim 1 , wherein the dielectric material is a resin material.

5. The electronic device according to claim 1 , wherein the noise source is a circuit board.

6. An electronic device described in any one of claims 1 to 5, which is an in-vehicle camera.

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