JP2004103757A - Emi reducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EMI reducing device which reduces EMI in the circumference of a cable in a simple constitution. <P>SOLUTION: An FFC 34 is inserted into a ferrite core 52 to reduce the EMI due to the FFC. With the elastic force of a spring part of a 2nd sheet metal member, the FFC 34 is pressed against a presser part of the 2nd sheet metal member with a ground potential and a 1st sheet metal member with the ground potential to further reduce the EMI due to the FFC 34. The 1st sheet metal member 24 and 2nd sheet metal member 38 are capable of restraining the ferrite core 52 to a specified position and cooperatively clamping the FFC 34, and locked with the elastic force of a spring part of the 2nd sheet metal member 38. Consequently, the EMI reducing device is realized having a simple constitution of three components, i.e. the 1st sheet metal member 24, 2nd sheet metal member 38, and ferrite core 52. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement in EMC (Electromagnetic Compatibility) of an electronic device, and more particularly to an EMI reduction device that reduces EMI (Electromagnetic Interference) around a cable with a ferrite core or the like.
[0002]
[Prior art]
Conventionally, it is known that EMI caused by the cable is reduced by inserting the cable through the ferrite core. Further, a technique for fixing a ferrite core to a substrate or the like with a simple structure has been proposed (for example, see Patent Documents 1 and 2).
[0003]
In general, the circuit elements on the board are covered with a metal plate at the ground potential to prevent the spread of fire when the circuit elements mounted on the board are ignited and to reduce EMI. It is known that EMI caused by a cable connected to a circuit element on a substrate is reduced by bringing the cable into close contact with the metal plate (for example, see Patent Document 3).
[0004]
[Patent Document 1]
JP-A-11-261276 [Patent Document 2]
Japanese Patent Application Laid-Open No. 2000-309139 [Patent Document 3]
JP-A-6-29198 [0005]
[Problems to be solved by the invention]
However, according to the techniques disclosed in Patent Documents 1, 2, and 3, EMI is reduced by inserting a cable into a ferrite core and adhering the cable to a ground potential metal plate to cover circuit elements on the board with the ground potential metal plate. In order to reduce the number of components, the number of parts increases in order to fix the cable, the ferrite core, and the metal plate in an appropriate position and in an appropriate configuration, and the labor for assembling and disassembling increases.
[0006]
An object of the present invention is to provide an EMI reduction device that reduces EMI around a cable with a simple configuration.
[0007]
[Means for Solving the Problems]
The EMI reduction device according to claim 1, wherein the conductive first sheet metal member having a hook hole and a locking portion is fixed in a posture covering a circuit element mounted on the substrate and electrically connected to the cable, and a spring portion. A hook portion locked by the hook hole, an engaging portion locked by the locking portion while being pulled by the spring portion, and a hook portion formed between the hook portion and the engaging portion. A conductive second sheet metal member having a holding portion that faces the first sheet metal member with the cable interposed therebetween and presses against the cable when the engaging portion is locked by the locking portion; and the first sheet metal. A ferrite core that is restricted by one or both of the member and the second sheet metal member and through which the cable is inserted.
[0008]
According to the EMI reduction device of the first aspect, the EMI caused by the cable is reduced by inserting the cable into the ferrite core. Also, if the first sheet metal member and the second sheet metal member are set to the ground potential, the elastic force of the spring portion of the second sheet metal member causes the cable to be connected to the holding portion of the second sheet metal member at the ground potential and the first sheet metal member at the ground potential. The pressure contact further reduces EMI due to the cable. According to the EMI reduction device of the first aspect, the first sheet metal member and the second sheet metal member can restrain the ferrite core at a predetermined position, and can cooperate or independently hold the cable. Are locked together by the elastic force of the spring portion of the second sheet metal member. Therefore, according to the EMI reduction device of the first aspect, EMI around the cable can be reduced with a simple configuration.
[0009]
One of the locking portion and the engaging portion of the EMI reduction device according to claim 2 has a hole, and the other has a boss fitted into the hole.
According to the EMI reduction device according to claim 2, the first sheet metal member and the second sheet metal member are locked to each other by locking the hook portion in the hook hole and fitting the boss in the hole, so that assembly and disassembly are performed. Easy.
[0010]
A longitudinal edge of the holding portion of the EMI reduction device according to claim 3 is bent to a side away from the first sheet metal member.
According to the EMI reduction device of the third aspect, it is possible to prevent the cable from being damaged at the edge of the second sheet metal member.
[0011]
The engaging portion of the EMI reduction device according to claim 4 has a handle portion bent to a side away from the first sheet metal member.
According to the EMI reduction device of the fourth aspect, since the second sheet metal member can be attached to and detached from the first sheet metal member by gripping the handle portion, assembly and disassembly are easy.
[0012]
The ferrite core of the EMI reduction device according to claim 5 is characterized in that the ferrite core is restrained on a side of the holding portion opposite to the cable.
According to the EMI reduction device according to the fifth aspect, the ferrite core can be installed in a narrow place, so that the size can be reduced.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described based on a plurality of examples.
(First embodiment)
FIG. 1 is a perspective view showing an EMI reduction device 1 according to a first embodiment of the present invention. The EMI reduction device 1 includes the first sheet metal member 24, the second sheet metal member 38, and the ferrite core 52.
[0014]
The first sheet metal member 24 is formed by pressing a metal plate. Since the first sheet metal member 24 is required to have fire resistance and conductivity, the material is preferably aluminum or the like. The first sheet metal member 24 is fastened to the substrate 40 by screws 72 (see FIG. 4). The width of the shield part 26 constituting the ceiling of the first sheet metal member 24 is large enough to cover most of circuit elements such as IC chips and wiring patterns (not shown) mounted on the substrate 40.
[0015]
Since the edge portion 54 of the first sheet metal member 24 is bent substantially perpendicularly to the shield portion 26, a bent portion 56 is formed between the shield portion 26 and the edge portion 54. The shield part 26 is supported by the edge part 54 in a posture parallel to the substrate 40 at a height separated from the circuit element mounted on the substrate 40.
[0016]
In the shield part 26 of the first sheet metal member 24, a hook hole 30 is formed by punching. The hook hole 30 has an elongated shape whose longitudinal axis is parallel to the ridge line of the bent portion 56 and penetrates through the shield portion 26.
[0017]
The boss 42 as an engaging portion is formed on the edge 54 of the first sheet metal member 24. The boss 42 is formed in a cylindrical shape by extrusion. The boss 42 and the hook hole 30 are located on an imaginary line extending on the surface of the first sheet metal member 24 from one point on the ridge line of the bent portion 56 in two directions perpendicular to the ridge line.
[0018]
The restraining portion 16 for restraining the ferrite core 52 at a predetermined position in cooperation with the second sheet metal member 38 projects from the shield part 26 of the first sheet metal member 24. The constraining portion 16 is formed by punching and bending, and the base end portion 12 is bent substantially perpendicularly to the shield portion 26 in a direction away from the substrate 40, and further, the distal end portion 14 is substantially bent with respect to the base end portion 12. It is bent vertically. The distal end portion 14 is supported by the base end portion 12 in a posture substantially parallel to the shield portion 26 at a height separated from the shield portion 26. The ferrite core 52 is restrained in the gap between the tip portion 14 and the shield portion 26.
[0019]
The ferrite core 52 is desirably provided near the connector 36 of the flexible flat cable (FFC) 34. This is because the effect of reducing the EMI is increased by blunting the waveform of the signal transmitted by the FFC 34 near the signal output source. The ferrite core 52 is formed in a substantially rectangular parallelepiped annular shape. The ferrite core 52 has a through-hole 50 having an elongated cross-sectional shape into which the FFC 34 is inserted. The ferrite core 52 is placed on the shield part 26 such that the axis of the through hole 50 is parallel to the shield part 26 of the first sheet metal member 24.
[0020]
The second sheet metal member 38 is formed by pressing a metal plate. Since the second sheet metal member 38 is required to have conductivity and elasticity, the material is preferably stainless steel or the like. The second sheet metal member 38 is formed with the pressing portions 29 and the engaging portions 44 arranged in an L shape with the spring portion 48 interposed therebetween. A hook portion 60 (see FIG. 2) is formed on the side of the pressing portion 29 opposite to the spring portion. The restraining portion 22 for restraining the ferrite core 52 in a direction perpendicular to the arrangement direction of the spring portion 48, the pressing portion 29, and the hook portion 60 extends from the pressing portion 29. Hereinafter, these elements constituting the second sheet metal member 38 will be described in detail.
[0021]
2A to 2C are perspective views of the second sheet metal member 38 viewed from three directions. Here, when describing the second sheet metal member 38, a reference direction is determined. A plane including the longitudinal axis and the transverse axis of the flat part 27 of the holding part 29 is defined as a horizontal plane, a direction perpendicular to the horizontal plane is defined as a vertical direction, and a direction in which the hook 60 is bent is defined as a downward direction.
[0022]
The holding portion 29 includes a flat portion 27 having a flat rectangular shape and a protection portion 28. When the second sheet metal member 38 is assembled to the first sheet metal member 24, the flat part 27 faces the shield part 26 of the first sheet metal member 24 with the FFC 34 interposed therebetween, and holds the FFC 34 together with the shield part 26. It is. The hook portion 60 is adjacent to one of the flat portions 27 in the longitudinal direction, and the spring portion 48 is adjacent to the other. The protection portion 28 is gently bent upward from the longitudinal edge of the flat portion 27 in an acute angle direction. The protection section 28 prevents the FFC 34 from being damaged at the corner of the second sheet metal member 38 when the second sheet metal member 38 is assembled.
[0023]
The hook portion 60 is gently bent downward from an end in the longitudinal direction of the pressing portion 29 in an acute angle direction. The hook portion 60 has a shape that can be inserted into the hook hole 30. When the hook portion 60 is pulled toward the holding portion 29 with the hook portion 60 inserted into the hook hole 30, the shield portion 26 of the first sheet metal member 24 fits inside the hook portion 60. When the shield part 26 of the first sheet metal member 24 fits inside the hook part 60, the end of the second sheet metal member 38 on the hook part side is restricted from moving in the direction perpendicular to the shield part 26.
[0024]
The spring portion 48 includes a first flat portion 68, a bent portion 66, and a second flat portion 64. The spring portion 48 is gently bent at the bent portion 66 in the acute angle direction. The first flat portion 68 is adjacent to the pressing portion 29 and is bent upward from the pressing portion 29 in an obtuse angle direction. The positioning portion 62 extends downward from the first flat portion 68 in a substantially vertical direction. The second flat portion 64 is adjacent to the engaging portion 44. The engagement portion 44 is bent from the second flat portion 64 in an obtuse angle direction and extends downward. Each bending is performed so that the first virtual plane including the lower surface of the flat portion 27 of the pressing portion 29 and the second virtual plane including the inner surface of the engaging portion 44 (the surface close to the pressing portion 29) intersect substantially perpendicularly. The bending angle of the part is set. Also, the first flat portion 68 and the pressing portion 29 are located such that the bent portion 66 between the first flat portion 68 and the second flat portion 64 is located away from the first virtual plane and the second virtual plane. The bending angle between the bending portion 69 and the bending portion 63 between the second flat portion 64 and the engaging portion 44 is set.
[0025]
The engagement portion 44 extends downward from the lower end of the spring portion 48. The engaging portion 44 has a flat portion 45 in which a hole 58 in which the boss 42 is fitted is formed, and a handle portion 46 which is bent vertically outward from the flat portion 45 (far from the pressing portion 29). The hole 58 is formed in a circular shape by punching.
[0026]
The constraining portion 22 includes a slope portion 20, a ceiling portion 18, and a side wall portion 70. The slope portion 20 is bent upward at an obtuse angle from the longitudinal edge of the flat portion 27 of the pressing portion 29. The ceiling portion 18 is bent in an obtuse angle direction from the upper edge of the slope portion 20 and extends in the horizontal direction. When the second sheet metal member 38 is locked to the first sheet metal member 24, the ceiling 18 is supported in a horizontal posture at a height away from the shield part 26 of the first sheet metal member 24. The vertical movement of the ferrite core 52 is restricted by the ceiling 18 and the shield 26. The side wall 70 is bent substantially vertically downward from an edge near the hook 60 of the ceiling 18. When the second sheet metal member 38 is locked to the first sheet metal member 24, the horizontal movement of the ferrite core 52 by the restraining portion 16 of the first sheet metal member 24 and the slope 20 and the side wall 70 of the second sheet metal member 38. Is regulated. In the present embodiment, no element is provided to restrict the horizontal movement of the ferrite core 52 in opposition to the inclined surface portion 20. However, the element may be appropriately provided according to the configuration of members provided around the ferrite core 52. . Further, the constrained portions 16 and 22 may or may not be pressed against the ferrite core 52.
[0027]
The configuration of the EMI reduction device according to the first embodiment has been described above. Next, an example of use of the EMI reduction device 1 according to the first embodiment will be described. FIG. 3 is a plan view showing the internal structure of the image input / output device 2 including the EMI reduction device 1. FIG. 4 is a partially enlarged view of FIG.
[0028]
The image input / output device 2 is an electronic device that functions as a scanner and a printer. The FFC 34 is a cable that transmits a drive signal and an output signal of an image sensor (not shown). On the substrate 40, a control circuit for controlling an image sensor, a printer head, a paper transport mechanism, and the like, an image processing circuit for processing an output signal of the image sensor, and the like are mounted. The connector 36 of the FFC 34 is connected to a connector (not shown) mounted on the board 40.
[0029]
The first sheet metal member 24 is fixed by a screw 72 at a position covering the circuit element mounted on the substrate 40. The first sheet metal member 24 is set to the ground potential by being in close contact with another metal member having the ground potential. The first sheet metal member 24 prevents the spread of fire when the circuit element mounted on the substrate 40 ignites, and reduces EMI caused by the circuit element mounted on the substrate 40.
[0030]
The ferrite core 52 is fixed near the connector 36 of the FFC 34 by the first sheet metal member 24 and the second sheet metal member 38. The FFC 34 extends from a substrate on which an image sensor (not shown) is mounted, and is inserted into the through hole 50 of the ferrite core 52. By inserting the FFC 34 through the ferrite core 52, EMI caused by the FFC 34 is reduced. The portion of the FFC 34 inserted into the ferrite core 52 is desirably covered with a conductor such as aluminum foil. The EMI caused by the FFC 34 is further reduced by covering the resin film covering the conductor of the FFC 34 with a conductive thin film such as an aluminum foil and bringing the conductive thin film into close contact with the first sheet metal member 24 and the second sheet metal member 38 at the ground potential. Is done.
[0031]
The FFC 34 is sandwiched between the connector 36 and the ferrite core 52 by the first sheet metal member 24 and the second sheet metal member 38. The method of assembling the second sheet metal member 38 to the first sheet metal member 24 is as follows.
[0032]
First, the ferrite core 52 into which the FFC 34 has been inserted is placed on the upper surface of the shield part 26 of the first sheet metal member 24, and the connector 36 of the FFC 34 is connected to the connector of the board 40.
[0033]
Next, while the holding part 29 of the second sheet metal member 38 is inclined with respect to the shield part 26 of the first sheet metal member 24, the hook part 30 of the second sheet metal member 38 is inserted into the hook hole 30 formed in the first sheet metal member 24. Insert 60. At this time, the ferrite core 52 is surrounded by the restraining portion 16 of the first sheet metal member 24 and the restraining portion 22 of the second sheet metal member 38, and the FFC 34 is sandwiched between the shield portion 26 and the pressing portion 29.
[0034]
Next, the handle portion 46 is pinched and the engaging portion 44 is pulled so that the FFC 34 is in close contact with the pressing portion 29 and the shield portion 26, and the boss 42 of the first sheet metal member 24 is inserted into the hole 58 of the engaging portion 44. . At this time, since the hook 60 serves as a fulcrum, a force is exerted to bring the holding portion 29 into close contact with the shield portion 26. At this time, the positioning of the hole 58 and the boss 42 is facilitated by bringing the positioning part 62 into contact with the shield part 26.
[0035]
When the boss 42 of the first sheet metal member 24 is inserted into the hole 58 of the engaging part 44, the engaging part 44 is moved to the edge of the first sheet metal member 24 by the restoring force of the spring 48 of the first sheet metal member 24. Adhere to 54. Also, the inner peripheral wall forming the hole 58 of the engaging portion 44 comes into pressure contact with the outer peripheral wall of the boss 42 by the restoring force of the spring portion 48 of the first sheet metal member 24. Therefore, when the boss 42 of the first sheet metal member 24 is inserted into the hole 58 of the engaging portion 44, thereafter, unless an external force that pulls the engaging portion 44 away from the edge 54 acts, the second sheet metal member The first sheet metal member 24 does not fall off from 38. Further, since the hook 60 and the engaging portion 44 come into close contact with the first sheet metal member 24, the second sheet metal member 38 is at the ground potential. When the second sheet metal member 38 is detached from the first sheet metal member 24, the handle portion 46 may be pulled in a direction to separate the engaging portion 44 from the edge portion 54.
[0036]
When the second sheet metal member 38 is assembled to the first sheet metal member 24 by the method described above, the ferrite core 52 is connected to the connector 36 of the FFC 34 by the restraining portion 16 of the first sheet metal member 24 and the restraining portion 22 of the second sheet metal member 38. A portion near the connector 36 of the FFC 34 is fixed in the vicinity, and is positioned by the first sheet metal member 24 and the second sheet metal member 38. The FFC 34 is in close contact with the first sheet metal member 24 at the ground potential and the second sheet metal member 38 at the ground potential.
[0037]
(Second embodiment)
FIG. 5 is a perspective view showing the second sheet metal member 80 and the ferrite core 52 of the EMI reduction device according to the second embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
[0038]
The second sheet metal member 80 is formed with a restraining portion 78 having a ceiling 18, a slope 20, and three side walls 70, 74, 76. The side wall portions 70 and 74 face each other with the ferrite core 52 interposed therebetween. The side wall 76 faces the slope 20 with the ferrite core 52 interposed therebetween. According to the EMI reduction device according to the second embodiment, the inclined portion 20 formed on the restraining portion 78 of the second sheet metal member 80 and the three side walls 70, 74, 76 are arranged along the shield portion 26 of the first sheet metal member 24. The movement of the ferrite core 52 in the direction perpendicular to the shield part 26 can be restricted by the ceiling 18 of the restraining part 78 in the direction in which the ferrite core 52 moves. There is no need to form a part that restrains
[0039]
(Third embodiment)
FIG. 6 is a perspective view showing the second sheet metal member 94 and the ferrite core 52 of the EMI reduction device according to the third embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
[0040]
The holding section 90 is composed of a flat section 86 and protection sections 88 and 84. The protective portions 88 and 84 are bent substantially vertically upward from both side edges in the longitudinal direction of the flat portion 86 (the reference direction is based on the first embodiment). The height of the protection portions 88 and 84 is set lower than the thickness of the annular portion of the ferrite core 52, that is, the height from the flat portion 86 to the through hole 50. Thereby, contact between the tips of the protection portions 88 and 84 and the FFC 34 can be prevented.
[0041]
The restraining portions 82 and 92 are bent upward in a substantially vertical direction from the flat portion 86 of the pressing portion 90, and are curved such that their tips approach each other. The distance between the upper portion of the constraint portion 82 and the upper portion of the constraint portion 92 is smaller than the length of the longitudinal axis of the ferrite core 52. Therefore, the ferrite core 52 is held between the restraining portions 82 and 92 and the flat portion 86 of the pressing portion 90 by the elastic force of the restraining portions 82 and 92, and is positioned on the upper surface of the pressing portion 90. For this reason, the ferrite core 52 can be installed in a narrow place.
[0042]
The FFC 34 is folded back by the protection portion 88, one of which is inserted into the ferrite core 52 with the folded portion interposed therebetween, and the other is sandwiched between the holding portion 90 and the shield portion 26.
[0043]
According to the plurality of embodiments of the present invention described above, the EMI caused by the FFC is reduced by inserting the FFC into the ferrite core. According to a plurality of embodiments of the present invention, the cable is pressed against the holding portion of the second sheet metal member at the ground potential and the first sheet metal member at the ground potential by the elastic force of the spring portion of the second sheet metal member. Is further reduced.
[0044]
Further, according to a plurality of embodiments of the present invention, the first sheet metal member and the second sheet metal member can restrain the ferrite core in a predetermined position, and can cooperate or independently clamp the cable. Then, they are locked to each other by the elastic force of the spring portion of the second sheet metal member. For this reason, according to the plurality of embodiments of the present invention, it is possible to realize an EMI reduction device having a simple configuration including three parts, that is, the first sheet metal member, the second sheet metal member, and the ferrite core.
[0045]
In the above-described embodiment, the structure in which the first sheet metal member and the second sheet metal member are locked to each other by fitting the boss and the hole has been described. However, for example, a hook formed by folding and a hole formed by punching The first sheet metal member and the second sheet metal member may be locked to each other by the engagement, or a pin may be inserted into holes formed in both members.
[0046]
In the above-described embodiment, an example in which the EMI reduction device is incorporated in an image input / output device is described. However, any electronic device including a cable for transmitting a high-frequency signal may be incorporated in any electronic device. Also, the type of cable is not limited to FFC.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an EMI reduction device according to a first embodiment of the present invention.
FIG. 2 is a perspective view showing a second sheet metal member according to the first embodiment of the present invention.
FIG. 3 is a plan view showing the internal structure of the image input / output device including the EMI reduction device according to the first embodiment of the present invention.
FIG. 4 is a partially enlarged view of FIG. 3;
FIG. 5 is a perspective view showing a second sheet metal member and a ferrite core according to a second embodiment of the present invention.
FIG. 6 is a perspective view showing a second sheet metal member and a ferrite core according to a third embodiment of the present invention.
[Explanation of symbols]
1 EMI reduction device 22, 78, 82, 92 Restraining part 24 First sheet metal member 29, 90 Pressing part 30 Hook 34 FFC (flexible flat cable)
38, 80, 94 Second sheet metal member 38 Second sheet metal member 40 Substrate 42 Boss 44 Engagement part 46 Handle part 48 Spring part 52 Ferrite core 58 Hole 60 Hook part

Claims (5)

A conductive first sheet metal member having a hook hole and a locking portion, which is fixed in a posture covering a circuit element mounted on the substrate and electrically connected to the cable,
A spring portion, a hook portion locked by the hook hole, an engaging portion locked by the locking portion in a state of being pulled by the spring portion, and between the hook portion and the engaging portion. A conductive second sheet metal member having a holding portion formed and opposed to the first sheet metal member with the cable interposed therebetween and having a pressing portion pressed against the cable when the engaging portion is locked by the locking portion;
A ferrite core through which the cable is inserted, which is constrained by one or both of the first sheet metal member and the second sheet metal member,
An EMI reduction device, comprising: The EMI reduction device according to claim 1, wherein one of the locking portion and the engaging portion has a hole, and the other has a boss fitted into the hole. 3. The EMI reduction device according to claim 1, wherein a longitudinal edge of the pressing portion is bent to a side separated from the first sheet metal member. 4. 4. The EMI reduction device according to claim 1, wherein the engagement portion has a handle portion bent to a side away from the first sheet metal member. 5. The EMI reduction device according to any one of claims 1 to 4, wherein the ferrite core is restrained on a side of the pressing portion opposite to the cable.

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