JP2023016364A - Electronic device - Google Patents

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: An electronic device 10 comprises: a noise generation source 12 which generates electromagnetic noise; and a housing 1. The housing has first and second housing components 16, 18 which define a housing space R for housing the noise generation source 12. The first housing component 16 includes: a first fixing part 16d; and two first inner wall parts 16f which extend in a direction away from the first fixing part 16d. The second housing component 18 includes: a second fixing part 18c which is fixed to the first fixing part 16d; and two second inner wall parts 18e which extend in a direction away from the second fixing part 18c, and which are arranged outside the two first inner wall parts 16f in a manner being aligned with them. At least one top surface of the two first inner wall parts 16f is provided with a cutout part 16g.SELECTED DRAWING: Figure 4

Description

The present disclosure relates to electronic equipment.

For example, Patent Literature 1 discloses an electronic device having a circuit board and a metal housing having an accommodation space for accommodating the circuit board. The housing includes a housing body that has an opening and accommodates the circuit board, and a lid that closes the opening of the housing body. An annular projection projecting toward the housing body is formed on the outer peripheral edge of the lid. An annular press-fitting groove into which the protrusion of the lid is press-fitted is formed in the opening edge of the housing body. The accommodation space is closed by press-fitting the ridges of the lid into the press-fitting grooves of the housing body, suppressing electromagnetic noise radiation (EMI) from the printed circuit board to the outside of the housing, and preventing electromagnetic noise from the outside. Malfunction immunity (EMS) of the printed circuit board is improved.

Japanese Utility Model No. 6-26295

By the way, 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 resonance can amplify the electromagnetic noise. As a result, electronic devices may radiate electromagnetic noise to the outside.

Therefore, in an electronic device having a noise source that generates electromagnetic noise and a housing that accommodates the noise source, the present disclosure is to make the resonance frequency of the housing different from the frequency of the electromagnetic noise generated from the noise source. is the subject.

In order to solve the above problems, 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 source;
the housing comprises first and second housing parts defining a receiving space for receiving the noise source;
The first housing component includes a first fixing portion fixed to the second housing component, and a first fixing portion protruding toward the second housing component and extending away from the first fixing portion. a first inner wall portion residing in the
The second housing component includes a second fixing portion fixed to the first fixing portion of the first housing component, and the second fixing portion projecting toward the first housing component. a second inner wall portion extending away from the first inner wall portion and arranged outside the first inner wall portion;
An electronic device is provided, wherein a notch is formed in the top surface of at least one of the two first inner walls.

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 resonance frequency of the housing is made different from the frequency of the electromagnetic noise generated from the noise source. can be done.

1 is an upper perspective view of an electronic device according to Embodiment 1 of the present disclosure; FIG. exploded perspective view of electronic equipment FIG. 2 is a bottom perspective view of the first housing part; Cross-sectional view of the electronic device along line AA in FIG. Cross-sectional view of the electronic device along line BB in FIG. Lower perspective view of the first housing component in the electronic device of the comparative example Upper perspective view of the second housing component in the electronic device of the comparative example Cross-sectional view of an electronic device of a comparative example Top view showing the electric field distribution in the electronic device of the comparative example Frequency-EMI characteristic diagram showing the shift of the resonance frequency of the housing An upper perspective view of an electronic device according to Embodiment 2 of the present disclosure exploded perspective view of electronic equipment FIG. 2 is a bottom perspective view of the first housing part; Cross-sectional view of the electronic device along line CC in FIG. Cross-sectional view of the electronic device along line DD in FIG. Frequency-EMI characteristic diagram showing another shift in housing resonance frequency Frequency-EMI diagram showing yet another shift in housing resonance frequency FIG. 11 is a bottom perspective view of a first housing component in an electronic device according to another embodiment of the present disclosure; Frequency-EMI diagram showing yet another shift in housing resonance frequency

Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of substantially the same configurations may be omitted. This is to avoid unnecessary verbosity in the following description and to facilitate understanding by those skilled in the art.

It is to be noted that the inventors provide the accompanying drawings and the following description for a full understanding of the present disclosure by those skilled in the art, which are intended to limit the subject matter of the claims. not a thing

(Embodiment 1)
FIG. 1 is an upper perspective view of an electronic device according to Embodiment 1 of the present disclosure. Also, FIG. 2 is an exploded perspective view of the electronic device. The XYZ orthogonal coordinate system shown in the drawing is for facilitating understanding of the embodiments of the present disclosure, and is not intended to limit the embodiments of the present disclosure.

As shown in FIGS. 1 and 2, the electronic device 10 according to the first embodiment of the present disclosure is, for example, a vehicle-mounted compact camera mounted on a vehicle. The electronic device 10 has a circuit board 12 that is a source of electromagnetic noise, and a housing 14 that is made of a conductive material such as a metal material and accommodates the circuit board 12 . The housing 14 is cuboid-shaped and comprises a first housing part 16 and a second housing part 18 .

Figure 3 is a bottom perspective view of the first housing part; 4 is a cross-sectional view of the electronic device taken along line AA of FIG. 1. FIG. 5 is a cross-sectional view of the electronic device taken along line BB in FIG.

As shown in FIGS. 4 and 5, the first housing component 16 and the second housing component 18 define a receiving space R for receiving the circuit board 12 by engaging with each other. Specifically, in the case of the first embodiment, the first housing component 16 has a substantially cylindrical shape with a bottom, and has a rectangular plate-like base portion 16a and a second housing part 16 extending from the outer peripheral edge of the base portion 16a. and a side wall 16b projecting toward part 18. As shown in FIG. The second housing component 18 has a substantially cylindrical shape with a bottom, and includes a rectangular plate-shaped base portion 18a and a side wall 18b projecting from the outer peripheral edge of the base portion 18b toward the first housing component 16. there is The side walls 16b of the first housing part 16 and the side walls 18b of the second housing part 18 face each other at their respective top surfaces. The engagement of the first housing part 16 and the second housing part 18 with each other results in the base portion 16a, side wall 16b of the first housing part 16, and the base portion 18a, side wall 18b of the second housing part 18. An enclosed accommodation space R is defined.

In addition, in the case of the first embodiment, the circuit board 12 is fixed to the base portion 18 a of the second housing component 18 via a plurality of fixing screws 20 . As a result, the circuit board 12 is electrically grounded to the second housing component 18 (the potential of the second housing component 18 becomes the same as the ground potential of the circuit board 12). Also, if the electronic device 10 is a miniature camera, an optical element such as a lens is attached to the second housing component 18 . A connection cable 22 (cable including a power cable and a signal cable) that connects the circuit board 12 and an external device (not shown) passes through a through hole 16c formed in the base portion 16a of the first housing component 16. .

The first and second housing parts 16, 18 are made from an electrically conductive material such as a metallic material. In the case of this first embodiment, the first and second housing parts 16, 18 are made from aluminum die casting (ADC 12). As a result, radiation of electromagnetic noise generated from the circuit board 12 to the outside of the electronic device 10 (EMI: Electromagnetic Interference) is suppressed, and malfunction resistance (EMS: Electromagnetic Susceptibility) of the circuit board 12 due to electromagnetic noise from the outside is suppressed. improves.

Moreover, in the case of the first embodiment, the first and second housing parts 16 and 18 are fixed to each other via a plurality of fixing screws 24 .

Specifically, side wall 16b of first housing component 16 includes first securing portion 16d that is secured to second housing component 18 . The side wall 18b of the second housing component 18 also includes a second fixing portion 18c that is fixed to the first fixing portion 16d of the first housing component 16. As shown in FIG.

In the case of the first embodiment, the first fixing portion 16d is formed on the rectangular side wall 16b of the first housing component 16 when viewed from the engagement direction of the first and second housing components 16 and 18 (in the Z-axis direction). view), and two are arranged diagonally. Similarly, two second fixing portions 18 c are arranged diagonally on the rectangular side wall 18 b of the second housing part 18 .

Further, in the case of the first embodiment, the first fixing portion 16d of the first housing component 16 is formed with a through hole 16e through which the fixing screw 24 passes. The second fixing portion 18c of the second housing component 18 is formed with a female threaded hole 18d into which the fixing screw 24 is screwed. The fixing screw 24 passes through the through hole 16e of the first fixing portion 16d and is screwed into the female threaded hole 18d of the second fixing portion 18c, thereby connecting the first fixing portion 16d and the second fixing portion 18c. are fixed and connected in direct current. Alternatively, a female screw hole may be formed in the first fixing portion 16d and a through hole may be formed in the second fixing portion 18c.

In addition, in the case of the first embodiment, the first housing component 16 and the second housing component 18 are made of aluminum die-cast and alumite-treated. Therefore, since the contact surfaces of the first fixing portion 16d and the second fixing portion 18c are covered with an oxide film, they are not DC-connected. However, the first fixing portion 16d and the second fixing portion 18c are DC-connected via a fixing screw 24 made of a conductive material such as a metal material. That is, the head portion 24a of the fixing screw 24 is in contact with the first fixing portion 16d and is connected in a direct current manner, and the shaft portion 24b of the fixing screw 24 having an external thread is engaged with the second fixing portion 18c. It is screwed into the screw hole 18d and connected in direct current. The portion of the first fixing portion 16d that contacts the head 24a of the fixing screw 24 has its oxide film scraped off by the rotation of the head 24a when the fixing screw 24 is tightened. can be connected in direct current with Further, since the female threaded hole 18d is formed by tapping after anodizing treatment, it can be directly connected to the shaft portion 24b of the fixing screw 24. As shown in FIG.

In the case of the first embodiment, the side wall 16b of the first housing component 16 protrudes toward the second housing component 18 and separates from each of the plurality of first fixing portions 16d (X-axis direction or It has a first inner wall portion 16f extending in the Y-axis direction). Specifically, two first inner wall portions 16f extend in a direction away from one first fixing portion 16d. In the case of Embodiment 1, the plurality (four) of first inner wall portions 16f are connected to each other to form one annular inner wall portion.

In addition, in the case of the first embodiment, the side wall 18b of the second housing component 18 protrudes toward the first housing component 16 while leaving the plurality of second fixing portions 18c (in the X-axis direction). or Y-axis direction). Specifically, two second inner wall portions 18e extend in a direction away from one first fixing portion 18c. In the case of Embodiment 1, the plurality (four) of the second inner wall portions 18e are connected to each other to form one annular inner wall portion. The inner wall portion 18e is arranged outside the first inner wall portion 16f of the first housing component 16 with a gap therebetween. Note that when the surfaces of the first and second housing parts 16 and 18 are covered with an oxide film (insulating layer), even if the second inner wall portion 18e is in contact with the first inner wall portion 16f, good.

Furthermore, in the case of the first embodiment, the top surface of at least one of the plurality of first inner wall portions 16f of the side wall 16b of the first housing component 16 is formed with the notch portion 16g. In the case of , a notch portion 16g is formed in each of the plurality of first inner wall portions 16f.

The notch portion 16g is a groove extending from the inside of the housing 14 toward the outside and divides the top surface of the first inner wall portion 16f. Further, in the case of the first embodiment, the notch portion 16b is formed at the center of the first inner wall portion 16f in the extending direction (X-axis direction or Y-axis direction).

The existence of the notch 16g makes it possible to make the resonance frequency of the housing 14 different from the frequency of the electromagnetic noise. This will be specifically described with reference to comparative examples.

FIG. 6 is a bottom perspective view of the first housing component in the electronic device of the comparative example. Moreover, FIG. 7 is a top perspective view of the second housing component in the electronic device of the comparative example. Furthermore, FIG. 8 is a cross-sectional view of an electronic device of a comparative example. Furthermore, 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 of the resonance frequency of the housing.

As shown in FIGS. 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 second housing component 118 extending from the outer peripheral edge of the base portion 116a. and a side wall 116b protruding from the bottom. The second housing component 118 includes a rectangular plate-shaped base portion 118a and side walls 118b projecting from the outer peripheral edge of the base portion 118a toward the first housing component 116. As shown in FIG. The side walls 116b of the first housing component 116 and the side walls 118b of the second housing component 118 face each other at their respective top surfaces. The engagement of the first housing component 116 and the second housing component 118 with each other causes the base portion 116a and the side walls 116b of the first housing component 116 and the base portion 118a and the side walls 118b of the second housing component 118 to engage. A housing space R for housing the circuit board 12 is defined.

Further, in the electronic device 110 of the comparative example, the side wall 116b of the first housing component 116 includes a first fixing portion 116d fixed to the second housing component 118. As shown in FIG. The side wall 118b of the second housing component 118 also includes a second fixing portion 118c that is fixed to the first fixing portion 116d of the first housing component 116. As shown in FIG. The first fixing portion 116d and the second fixing portion 118c are fixed to each other via fixing screws 24. As shown in FIG.

Furthermore, in the electronic device 110 of the comparative example, the first fixing portion 116 d is formed on the rectangular side wall 116 b of the first housing component 116 when viewed from the engagement direction (Z When viewed in the axial direction), two are arranged diagonally. Similarly, two second fixing portions 118 c are arranged diagonally on the rectangular side wall 118 b of the second housing part 118 .

In the case of the electronic device 110 of the comparative example, in the side wall 116b of the first housing component 116, the second A plurality of first inner wall portions 116f are provided that protrude toward the housing component 116 and extend in a direction (X-axis direction or Y-axis direction) away from the plurality of first fixing portions 116d. Specifically, two first inner wall portions 116f extend in a direction away from one first fixing portion 116d. A plurality of (four) first inner wall portions 116f are connected to each other to form one annular inner wall portion.

Note that unlike the electronic device 10 of the first embodiment, the first inner wall portion 116f of the side wall 116b of the first housing component 116 does not have a notch in the electronic device 110 of the comparative example.

Further, in the case of the electronic device 110 of the comparative example, in the side wall 118b of the second housing component 118, the portion other than the second fixing portion 118c, i. A plurality of second inner wall portions 118e are provided that protrude toward one housing component 116 and extend in a direction (X-axis direction or Y-axis direction) away from the plurality of second fixing portions 118c. . Specifically, two second inner wall portions 118e extend in a direction away from one first fixing portion 118c. A plurality of (four) second inner wall portions 118e are connected to each other to form one annular inner wall portion. The second inner wall portion 118e is arranged outside the first inner wall portion 116f of the first housing component 116 with a gap therebetween. Note that when the surfaces of the first and second housing parts 16 and 18 are covered with an oxide film (insulating layer), even if the second inner wall portion 18e is in contact with the first inner wall portion 16f, good.

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

When such an electric field distribution occurs, the portions of the first and second housing parts 116, 118 where the electric field strength is high function as if they were a "dipole antenna". Specifically, the first fixing portion 116d and the second fixing portion 118c, which are fixed to each other via the fixing screw 24, function as a "feeding point" of the "dipole antenna". In addition, two first inner wall portions 116f extending away from the first fixing portion 116d and two second inner wall portions 116f extending away from the second fixing portion 118c function as the "feed point". The inner wall portion 118e functions as a "element" of a "dipole antenna" that receives electromagnetic noise. When the "dipole antenna" receives the electromagnetic noise generated from the circuit board 12, the housing 114 resonates.

In particular, as shown in FIG. 9, one side (that is, the side wall 114b) of the rectangular housing 114 is substantially is 1/4 of the wavelength λ of the frequency of the electromagnetic noise, the housing 114 resonates significantly. That is, two first inner wall portions 116f extending in a direction (X-axis direction or Y-axis direction) away from the first fixing portion 116d and a direction away from the second fixing portion 118c (X-axis direction) or Y-axis direction) is a quarter of the wavelength λ of the frequency of the electromagnetic noise, the housing 114 has the frequency of the electromagnetic noise has substantially the same resonant frequency as In other words, housing 114 comprises a "half-wave dipole antenna."

In order to suppress such resonance of the housing, in the electrical device 10 according to the first embodiment, the notch portion 16g is formed in the second inner wall portion 16f of the side wall 16b of the first housing component 16. there is

The frequency-EMI characteristic diagram in FIG. 10 is the result obtained by simulation, and the frequency of the electromagnetic noise radiated from the circuit board 12 is changed, thereby changing the electromagnetic noise (EMI) radiated from the housing. showing strength. In FIG. 10, the solid line indicates the intensity of electromagnetic noise radiated from the housing 114 of the electronic device 110 of the comparative example. Further, the dashed line indicates the intensity of electromagnetic noise emitted from the housing 14 of the electronic device 10 according to the first embodiment, and is the cutout portion formed in the first inner wall portion 16f of the first housing component 16. The strength is shown when the width w of 16g (the size in the extending direction of the inner wall portion 16f) is 3 mm. Furthermore, the dashed-dotted line indicates the intensity of electromagnetic noise radiated from the housing 14 of the electronic device 10 according to the first embodiment when the width w of the notch 16g is 5 mm.

10, in the housing 14 of the electronic device 10 according to the first embodiment, the width of the notch portion 16g formed in the first inner wall portion 16f of the first housing component 16 is As w increases, the peak value of the intensity of EMI radiated from the housing 14 shifts to the low frequency side, that is, the resonance frequency of the housing 14 shifts to the low frequency side. In addition, compared to the peak value of the intensity of EMI radiated from the housing 114 of the electronic device 110 of the comparative example in which the cutout portion 16g is not formed, the peak value of the first embodiment shifts to the low frequency side. .

It is considered that such a shift in the peak value of the intensity of EMI is caused by a change in the length of the "element" of the "dipole antenna" due to the notch 16g. In the first embodiment, as shown in FIG. 3, a portion ( The portion indicated by cross hatching) increases in total length. The term "insulator" as used herein refers to air, an oxide film, a seal member, and the like. Therefore, the length that functions as the "element" of the "dipole antenna" is increased. As a result, the peak value of the intensity of EMI radiated from the housing 14 shifts to the low frequency side, that is, the resonance frequency of the housing 14 shifts to the low frequency side. The inventors discovered through simulation how the frequency characteristics of the housing 14 change due to such cutouts.

Further, when the notch portion is provided as in this embodiment, not only does the peak value of the intensity of EMI radiated from the housing shift to the low frequency side, but the intensity of EMI radiated from the housing itself may decrease. It has the advantage of being flexible. This is because the radiation efficiency of electromagnetic waves can be expected to decrease at the corners of the notch.

Therefore, if a cutout portion 16g having an appropriate width w is provided at the center of the side wall 16b of the first housing component 16 in the extending direction of the first inner wall portion 16f, the resonance frequency of the housing 14 can be generated from the circuit board 12. can be different from the frequency of electromagnetic noise.

Further, like the electronic device 110 of the comparative example shown in FIG. Even if one side of the rectangular housing 14 at 10 (that is, the length in the extending direction of the side walls 16b and 18b) is substantially 1/4 of the wavelength λ of the electromagnetic noise frequency, the size of the housing 14 The resonance frequency of the housing 14 can be made different from the frequency of the electromagnetic noise generated from the circuit board 12 without changing .

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 resonance frequency of the housing must be different from the frequency of the electromagnetic noise generated from the circuit board. can let

(Embodiment 2)
The second embodiment is an improvement of the first embodiment. Therefore, the second embodiment will be described, focusing on the differences from the first embodiment.

FIG. 11 is a top perspective view of an electronic device according to Embodiment 2 of the present disclosure. Also, FIG. 12 is an exploded perspective view of the electronic device. Figure 13 is a bottom perspective view of the first housing part; 14 is a cross-sectional view of the electronic device taken along line CC of FIG. 11. FIG. 15 is a cross-sectional view of the electronic device taken along line DD in FIG.

As shown in FIGS. 11 and 12, an electronic device 210 according to Embodiment 2 of the present disclosure is made of a circuit board 212 that is a source of electromagnetic noise and a conductive material such as a metal material. and a housing 214 containing 212 . The housing 214 has a cuboid shape and comprises a first housing part 216 and a second housing part 218 .

In the case of the second embodiment, the first housing component 216 has a substantially cylindrical shape with a bottom, and includes a rectangular plate-shaped base portion 216a and a base portion 216a extending toward the second housing component 218 from the outer peripheral edge of the base portion 216a. and a projecting side wall 216b. The second housing component 218 has a substantially cylindrical shape with a bottom, and includes a rectangular plate-shaped base portion 218a and a side wall 218b projecting from the outer peripheral edge of the base portion 218a toward the first housing component 216. there is The circuit board 212 is fixed to the base portion 218 a of the second housing component 218 via a plurality of fixing screws 220 .

In the case of this second embodiment, the first and second housing parts 216 , 218 are fixed together via a plurality of fixing screws 224 . Specifically, side wall 216 b of first housing component 216 includes first securing portion 216 d that secures to second housing component 218 . The side wall 218b of the second housing component 218 also includes a second securing portion 218c that is secured to the first securing portion 218d of the first housing component 216. As shown in FIG.

The side wall 216b of the first housing component 216 is not fixed to the second housing component 218 except for the first fixing portion 216d. Similarly, the side wall 218 b of the second housing component 218 is not fixed to the first housing component 216 except for the second fixing portion 218 .

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

Further, in the case of the second embodiment, the side wall 218b of the second housing component 218 extends in the direction away from the second fixing portion 218c (X-axis direction or Y-axis direction), It has a plurality of grooves 218e into which the plurality of ridges 216f of 216 enter. Specifically, two grooves 218e extend in a direction away from one second fixing portion 218c.

Furthermore, in the case of the second embodiment, the notch portion 216g is formed on the top surface of at least one of the plurality of protrusions 216f of the side wall 216b of the first housing component 216. , the notch portion 16g is formed in each of the plurality of ridges 216f.

The notch portion 216g is a groove extending from the inside of the housing 214 toward the outside and divides the top surface of the ridge portion 216f. Further, in the case of the second embodiment, the notch portion 216b is formed at the center of the extending direction (X-axis direction or Y-axis direction) of the ridge portion 216f.

Furthermore, in the case of the second embodiment, the first fixing portion 216d of the first housing component 216 and the second fixing portion 218c of the second housing component 218 are not in direct contact, They are in contact through body 226 . The dielectric 226 is a member made of resin material, for example, and has a through hole 226a through which the shaft portion 224b of the fixing screw 224 passes.

The projection amount p of the protrusion 216f and the width w of the notch 216g on the side wall 216b of the first housing component 216, the depth d of the groove 218e on the side wall 218b of the second housing component 218, and the dielectric 226 By appropriately setting the height h, the resonance 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 .

Specifically, first, in order to realize the first shift of the resonance frequency, the protrusion amount p of the protrusion 216f on the side wall 216b of the first housing component 216 and the protrusion amount p on the side wall 218b of the second housing component 218 are The depth d of the groove 218e is appropriately set.

Moreover, in order to realize another shift of the resonance frequency, the width w of the notch 216g in the protrusion 216f of the side wall 216b of the first housing component 216 is appropriately set.

And, in order to achieve yet another resonant frequency shift, 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 Height h is set appropriately.

By implementing these three shifts of resonance frequencies in combination, the resonance frequency of housing 214 can be made different from the frequency of electromagnetic noise generated from circuit board 212 .

First, the shift of the resonance 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.

FIG. 16 is a frequency-EMI characteristic diagram showing another shift in the resonance frequency of the housing.

The frequency-EMI characteristic diagram in FIG. 16 is the result obtained by simulation, and the intensity of electromagnetic noise (EMI) radiated from the housing is changed by changing the frequency of the electromagnetic noise radiated from the circuit board. is shown. In FIG. 16, the solid line indicates the intensity of electromagnetic noise radiated from the housing 114 of the electronic device 110 of the comparative example. The dashed line indicates the intensity of electromagnetic noise radiated from the electronic device 210 according to the second embodiment from which the cutout portion 216g and the dielectric 226 are removed, and shows the intensity of the electromagnetic noise emitted from the groove in the side wall 218b of the second housing component 218. The strength is shown when the depth d of 218e is 2 mm. Furthermore, the dashed line indicates the intensity of electromagnetic noise emitted from the housing 214 of the electronic device 210 according to the second embodiment from which the notch 216g and the dielectric 226 are removed, and the depth d of the groove 218e is It shows the strength when it is 3 mm.

16, in the housing 214 of the electronic device 210 according to the second embodiment from which the notch 216g and the dielectric 226 are removed, the depth of the groove 218e of the second housing component 218 is As the value d increases, the peak value of the intensity of EMI radiated from the housing 214 shifts to the low frequency side, that is, the resonance frequency of the housing 214 shifts to the low frequency side. Also, the peak value of the intensity of EMI radiated from the housing 214 is lower than the peak value in the electronic device 110 of the comparative example.

Such a shift in the peak intensity of EMI opposes the insulator in the region where the first housing part and the second housing part engage, as shown in FIGS. 8 and 14. This is caused by differences in the surface areas S1, S2, S3, and S4 of the portions (enlarged portions indicated by thick lines). The term "insulator" as used herein refers to air, an oxide film, a seal member, and the like. That is, when the electronic device 210 according to the second embodiment and the electronic device 110 of the comparative example are compared, as shown in FIGS. The surface areas S1 and S2 of the portions that face each other are larger than the surface areas S3 and s4 of the portions that face each other at a short distance in the electronic device 110 of the comparative example. Also, the greater the depth d of the groove 218e of the side wall 218b of the second housing component 218, the greater the surface area of the portions facing each other at a short distance. The greater such surface area, the greater the capacitive coupling between the first housing part and the second housing part, thereby generating an electric field between the first housing part and the second housing part. Overall strength is reduced. As a result, the peak intensity of EMI radiated from the housing 214 shifts to the low frequency side, that is, the resonance frequency of the housing shifts to the low frequency side. The inventors found out such frequency characteristics with respect to the surface areas of the first and second housing parts 216 and 218 by simulation.

Therefore, if the protrusion amount p of the protrusion 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 are set appropriately, By appropriately setting the surface areas of the mating portions, the resonance frequency of the housing 214 can be made different from the frequency of the electromagnetic noise generated from the circuit board 212 .

Next, the shift of the resonance frequency of the housing 214 due to the width w of the notch 216g in the ridge 216f of the side wall 216b of the first housing component 216 will be described in the above first embodiment with reference to FIG. As I did.

Subsequently, the resonance frequency of the housing 214 due to the height h of the dielectric 226 arranged between the first fixed part 216d of the first housing part 216 and the second fixed part 218c of the second housing part 218 will be explained.

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

The frequency-EMI characteristic diagram in FIG. 17 is the result obtained by simulation, and the intensity of electromagnetic noise (EMI) radiated from the housing is changed by changing the frequency of the electromagnetic noise radiated from the circuit board. is shown. In FIG. 17, the solid line indicates the intensity of electromagnetic noise radiated from the housing 114 of the electronic device 110 of the comparative example. The dashed line represents the intensity of electromagnetic noise radiated from the housing 114 of the electronic device 110 of the comparative example provided with a dielectric, and represents the height h of the dielectric (that is, the distance between the first fixing portion 116d and the second fixing portion 116d) The strength is shown when the distance from the fixed portion 118c) is 2.5 mm. Furthermore, the dashed line indicates the intensity of electromagnetic noise radiated from the housing 114 of the electronic device 110 of the comparative example provided with the dielectric, when the height h of the dielectric is 4.5 mm. ing.

As shown by the dashed line and the dashed line in FIG. 17 , in the housing 114 of the electronic device 110 of the comparative example provided with the dielectric, when the height h of the dielectric increases, the intensity of EMI radiated from the housing 114 peaks. The value shifts to lower frequencies, that is, the resonance frequency of housing 114 shifts to lower frequencies. Along with that, the peak value also decreases. Moreover, compared to the peak value of the intensity of EMI radiated from the housing 114 of the electronic device 110 of the comparative example in which no dielectric is provided, the peak value is shifted to the low frequency side and decreased.

It is believed that such a shift in the peak value of EMI intensity is caused by the shaft portion of the fixing screw penetrating the dielectric functioning as an "inductance". In other words, the first fixing portion 116d of the first housing component 116 and the second fixing portion 118c of the second housing component 118 are electrically connected via "inductance". When the first housing component 116 and the second housing component 118 are electrically connected via the "inductance", the length of the "element" of the "dipole antenna" formed by the connection becomes long. . As a result, the peak value of the intensity of EMI radiated from the housing 114 shifts to the low frequency side, that is, the resonance frequency of the housing shifts to the low frequency side. The inventors found the frequency characteristic with respect to the inductance between the first and second housing parts 116 and 118 through simulation.

Further, when a dielectric is provided as in the second embodiment, not only does the peak value of the intensity of EMI radiated from housing 114 shift to the low frequency side, but also the intensity of EMI radiated from housing 114 itself decreases. It has the advantage of going down. This is because the radiation efficiency of the electromagnetic wave is lowered at the portion where the first fixing portion 116d or the second fixing portion 118c and the dielectric are in contact with each other.

Note that FIG. 17 shows a shift in resonance frequency when a dielectric is provided in the electronic device 110 of the comparative example shown in FIGS. Even when the dielectric 226 is provided between the first fixing portion 216c of the first housing component 216 and the second fixing portion 218d of the second housing component 218 as in the second embodiment, A similar resonance frequency shift is assumed to occur.

Therefore, if the first fixed portion 216d of the first housing component 216 and the second fixed portion 218c of the second housing component 218 are brought into contact via the dielectric 26 having an appropriate height h, the housing 214 can be made different from the frequency of electromagnetic noise generated from the circuit board 212 .

In the 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 resonance frequency of the housing is set to the electromagnetic noise generated from the circuit board. can be different from the frequency of

Although the present disclosure has been described above with reference to the first and second embodiments, the embodiments of the present disclosure are not limited to these.

For example, in the case of the first and second embodiments described above, the circuit board 12 is the noise source that is housed in the housing 14 and generates electromagnetic noise that can cause the housing 14 to resonate. However, in the embodiments of the present disclosure, the noise source is not limited to the circuit board. A noise source may be, for example, a sensor.

Further, in the case of the second embodiment described above, the dielectric 226 arranged between the first fixing portion 216d of the first housing component 216 and the second fixing portion 218c of the second housing component 218 is It is a member made from a resin material. However, embodiments of the present disclosure are not limited to this. The dielectric may be air, for example. In this case, the first fixing portion 216d and the second fixing portion 218c face each other with a gap therebetween. Dispersing the metal particles inside the dielectric lowers the radiation efficiency of electromagnetic waves, so there is an advantage that the intensity of EMI radiated from the housing 214 is further reduced.

Further, in the case of Embodiment 1 described above, in the first inner wall portion 16f of the side wall 16b of the first housing component 16, the notch portion 16g is arranged at the center in the extending direction of the first inner wall portion 16f. ing. However, the position on the first inner wall where the notch is arranged is not limited to the center.

18 is a bottom perspective view of a first first housing component in an electronic device according to another embodiment of the present disclosure; FIG. Also, FIG. 19 is a frequency-EMI characteristic diagram showing yet another shift in the resonance frequency of the housing.

FIG. 18 shows a first housing component 316 in an electronic device according to another embodiment. The electronic device according to another embodiment corresponds to the electronic device 110 of the comparative example shown in FIGS. 6 to 9 with a notch 316g. The notch portion 316g is formed in the first inner wall portion 316f of the side wall 316b of the first housing component 316, not at the center in the extending direction, but at a position shifted from the center. Specifically, a notch portion 316g is formed near a corner formed by connecting the two first inner wall portions 316f.

When the notch portion 316g is formed in the first inner wall portion 316f near the corner in this way, as shown in FIG. Compared to the peak value (solid line) of the electronic device 110 of the comparative example in which the notch portion is not formed, the peak value is shifted to the high frequency side.

It is considered that such a 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 notch. As described above, when the notch is formed apart from the corner, the total length of the opposed portions via the insulator is increased by the length of the rising portion and the falling portion of the notch. On the other hand, if the notch is formed near the corner, the notch exists at a location away from the first and second fixed parts, which are the feeding parts of the "dipole antenna". If there is a notch at a location distant from the power supply, the function of that location as an "element" is reduced. The effect of this decrease is greater than the effect of the increase in the total length of the facing portions via the insulator by the length of the rising portion and the falling portion of the notch. Thus, forming cutouts near the corners shortens the length of the "element". As a result, when the notch is formed near the corner, the peak value of the intensity of EMI radiated from the housing shifts to the high frequency side.

Therefore, even if cutout portion 16g is located near the corner of the housing in the above-described first embodiment, the resonance frequency of the housing can be made different from the frequency of the electromagnetic noise generated from the circuit board.

That is, in a broad sense, an electronic device according to an embodiment of the present disclosure includes a noise generation source that generates electromagnetic noise, and a housing that is made of a conductive material and accommodates the noise generation source. A housing includes first and second housing parts defining a housing space for housing the noise source, the first housing part being fixed to the second housing part and a first fixing part. , a first inner wall portion projecting toward the second housing part and extending away from the first fixing part, wherein the second housing part is connected to the first housing part; a second fixing portion fixed to the first fixing portion of a component; a second fixing portion projecting toward the first housing component and extending away from the second fixing portion; and a second inner wall portion arranged outside the first inner wall portion, and a notch portion is formed in the top surface of at least one of the two first inner wall portions.

As described above, the embodiment has been described as an illustration of the technology in the present disclosure. To that end, the accompanying drawings and detailed description have been provided. Therefore, among the components described in the attached drawings and detailed description, there are not only components essential for solving the problem, but also components not essential for solving the problem in order to illustrate the technology. can also be included. Therefore, it should not be immediately recognized that those non-essential components are essential just because they are described in the attached drawings and detailed description.

In addition, since the above-described embodiment is for illustrating the technology in the present disclosure, various changes, replacements, additions, omissions, etc. can be made within the scope of claims or equivalents thereof.

INDUSTRIAL APPLICABILITY The present disclosure is applicable to electronic equipment having a noise source that generates electromagnetic noise and a housing that accommodates the noise source.

10 electronic device 12 noise source (circuit board)
16 first housing part

16d First fixing portion 16f First inner wall portion 18 Second housing component 18c Second fixing portion 18e Second inner wall portion R Accommodation space

Claims (7)

a noise source that generates electromagnetic noise;
a housing made of a conductive material and containing the noise source;
the housing comprises first and second housing parts defining a receiving space for receiving the noise source;
The first housing component includes a first fixing portion fixed to the second housing component, and a first fixing portion protruding toward the second housing component and extending away from the first fixing portion. a first inner wall portion residing in the
The second housing component includes a second fixing portion fixed to the first fixing portion of the first housing component, and the second fixing portion projecting toward the first housing component. a second inner wall portion extending away from the first inner wall portion and arranged outside the first inner wall portion;
An electronic device, wherein a notch is formed in the top surface of the first inner wall.
2. The electronic device according to claim 1, wherein the length in the extending direction of said inner wall portion and said outer wall portion is 1/4 of the wavelength of the frequency of said electromagnetic noise.
Two of the first fixing portions are arranged diagonally on the first housing component,
2. The electronic device according to claim 1, wherein two of said second fixing portions are arranged diagonally on said second housing component.
4. The electronic device according to claim 3, wherein said notch portion is formed in the center of said first inner wall portion in the extending direction.
4. The electronic device according to claim 3, wherein said notch is formed near a corner formed by connecting said two first inner wall portions.
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 a female threaded hole is formed in the other;
2. The electronic device of claim 1, further comprising a fixing screw made of a conductive material, passing through the through hole and screwing into the female threaded hole.
2. The electronic device according to claim 1, wherein said noise source is a circuit board.

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