Abstract:
An EMC core supporting structure for supporting one or more EMC cores inside a casing, which accommodates a printed circuit board, includes a plate member capable of shielding electromagnetic waves. Preferably, the plate member expanding inside the casing to substantially cover the printed circuit board, and at least one side portion of the plate member is connected to an inner wall of the casing. A supporting portion that receives the EMC core (s) is formed on a surface of the plate member opposite to a surface facing the printed circuit board for mounting the at least one EMC core on the plate member.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a member for supporting an EMC (electromagnetic compatibility) ferrite core.  
           [0002]    Conventionally, for EMC use of devices, an EMC ferrite core has been widely used for preventing unintended electromagnetic radiation, which causes noises in electronic devices such as medical devices and OA appliances. In particular, cables that connect such electronic devices with external devices can be transmission channels of noise components. Thus, typically, at proximal end portions of the cables, which are connected to circuit boards, the EMC cores are used. The EMC cores are very important for preventing the noise components. However, they require dedicated securing structure, and the securing position inside the electronic devices is limited.  
           [0003]    [0003]FIG. 5A is a perspective view showing an inner structure of an circuit unit  90 , which is provided at a proximal end portion of a scope unit  50  of an electronic endoscope shown in FIG. 6. On a printed circuit board  89  inside the circuit unit  90 , a CCD driving circuit for supplying driving signals to a CCD provided at the distal end of the scope unit  50 , and a signal processing circuit that processes the output of the CCD are provided.  
           [0004]    The external connector  81  is used for connection with a processor unit, which processes the output of the CCD and generates a video signal. Through cables  86   c  and  87   c  connected to connectors  86  and  87  on the printed circuit board  89 , the processor unit is connected to the printed circuit board  89 . The processor unit accommodates a light source, which emits light to a light incident portion  80 . The light is directed through a light guide  75  to the tip end of the scope unit.  
           [0005]    A cable  88   c , which is connected to a connector  88  mounted on the printed circuit board  89 , is a cable including a bundle of signal transmission wires connected to the CCD, which is provided at the distal end portion of the scope unit. In some cases, an insertion portion  51  (see FIG. 6) of the scope unit is several meters long, and the signal cable  88   c  also has the same length. In order to prevent unnecessary radiation of electro magnetic wave inside the circuit unit  90 , the signal cable  88   c  is inserted through EMC cores  77  and  78 . The EMC cores  77  and  78  are secured inside the circuit unit  90 . For this purpose, as shown in FIG. 5B, which shows a cross section taken along line A-A′ of FIG. 5A, the EMC cores  77  and  78  are screwed on a side wall of a casing  100  using a supporting member  79 . The circuit unit  90  is covered with a shielding cover  82  made of metal, which prevents unintended radiation of an electromagnetic wave from the printed circuit board  89 .  
           [0006]    As described above, an EMC core generally requires a particular supporting member, which is to be provided inside an electronic device. Further, a position where the supporting member is mounted inside the electronic device is limited. Therefore, using an EMC core may impede design freedom and/or sometimes prevent downsizing of electronic devices.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention is advantageous in that an improved structure for securing an EMC core and a securing member used in such a structure are provided, which allows downsizing of devices, and provides improved design freedom.  
           [0008]    According to embodiments of the present invention, there is provided an EMC core supporting structure for supporting one or more EMC cores inside a casing which accommodates a printed circuit board. The EMC core supporting structure includes a plate member capable of shielding electromagnetic waves. Preferably, the plate member expands inside the casing to substantially cover the printed circuit board, and at least one side portion of the plate member is connected to an inner wall of the casing. A supporting portion that receives the EMC core(s) is formed on a surface of the plate member opposite to a surface facing the printed circuit board for mounting the at least one EMC core on the plate member.  
           [0009]    With this structure, since the plate member, which shields the electro-magnetic waves, is placed between the EMC core(s) and the printed circuit board, unintended or unnecessary electro-magnetic waves radiated from the printed circuit board will not reach the EMC core(s). Further, since the plate member functions for shielding the electromagnetic wave as well as for supporting the EMC core(s), it is not necessary to use an optional casing for shielding the printed circuit board.  
           [0010]    In one embodiment, at least one side portion of the plate member includes a portion which is bent to form a U-shaped portion having two parallel surfaces facing each other and a connecting portion that connects the two parallel surfaces, the connecting portion being secured to the inner wall of the casing. Therefore, it is not necessary to provide a separate member for supporting the EMC core(s).  
           [0011]    In a particular case, the at least one EMC core is held within a space defined by the two parallel surfaces and the connecting portion.  
           [0012]    It is possible to secure the at least one EMC core and the connecting portion together on the inner wall using screws.  
           [0013]    Alternatively, the at least one side portion of the plate member includes a portion that is bent to form an L-shaped portion, which is secured onto the inner wall of the casing.  
           [0014]    In this case, an EMC core receiving portion may be integrally provided on the plate member, the at least one EMC core being held by the EMC core receiving portion. The EMC core receiving portion may be provided at any portion on the plate member. Thus, design freedom is well increased.  
           [0015]    In a particular case, the EMC core receiving portion may have a U-shaped portion having two parallel surfaces and a connecting portion that connects the two parallel surfaces, the connecting portion being secured on the plate member, the at least one EMC core being held within a space defined by the two parallel surfaces and the connecting portion. Of course, any other configuration of the EMC core receiving portion can be employed.  
           [0016]    Optionally, the L-shaped portion is secured on the inner wall using screws.  
           [0017]    According to embodiments, only one side portion of the plate member is secured onto the inner wall, and an opposite side portion of the plate member may be bent to form a bent portion, which is bent toward the printed circuit board.  
           [0018]    According to another aspect, there is provided a circuit board shielding structure employed in a casing which accommodates a printed circuit board, the shielding structure including a plate member capable of shielding electromagnetic waves, the plate member expanding inside the casing to substantially cover the printed circuit board, the casing having at least side walls capable of shielding electro-magnetic waves, each of the side walls being substantially perpendicular to the surface of the printed circuit board, the side walls surrounding the printed circuit board, at least one side portion of the plate member being connected to an inner surface of one of the side walls, a supporting portion that receives at least one EMC core being formed on a surface of the plate member opposite to a surface facing the printed circuit board for mounting the at least one EMC core on the plate member.  
           [0019]    Optionally, the shielding structure may include a lower plate arranged on an opposite side of the plate member with respect to the printed circuit board, the lower plate being capable of shielding electromagnetic waves, the lower plate having an area covering the printed circuit board, the printed circuit board being shielded by the plate member, the side walls and the lower plate.  
           [0020]    According to another aspect, there is provided an EMC core supporting member having a plate member capable of shielding electromagnetic waves, a supporting portion for supporting an EMC core is formed on one surface of the plate member, a connection portion is formed on a side portion of the plate member, the connection portion being formed by bending the plate member.  
           [0021]    Further provided is an EMC core supporting member formed of a plate member capable of shielding electromagnetic waves, which includes a shielding portion, and an EMC core supporting portion which is formed by bending the plate member corresponding to an external shape of at least one EMC core so as to hold the at least one EMC core.  
           [0022]    Optionally, the supporting member is provided inside a casing of an electronic device, the EMC core supporting portion having an area contacting the casing, the EMC core supporting portion being secured to the casing at the area contacting the casing with screws.  
           [0023]    According to a further aspect, there Is provided a shielding structure for shielding a printed circuit board employed in an electronic device, including an EMC core supporting member arranged on one side of the printed circuit board, a shielding plate arranged on the other side of the printed circuit board. The EMC core supporting member formed of a plate member is capable of shielding electro-magnetic waves, the EMC core supporting member having a shielding portion and an EMC core supporting portion which is formed by bending the plate member corresponding to an external shape of at least one EMC core so as to hold the at least one EMC core, the EMC core supporting portion being formed on a surface of the EMC core supporting member opposite to a surface facing the printed circuit board.  
           [0024]    Optionally, a casing of the electronic device is made of metal, and the EMC core supporting member is electrically connected with the casing. 
       
    
    
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS  
       [0025]    [0025]FIGS. 1A and 1B schematically show a structure of an circuit unit employing an EMC core supporting member according to a first embodiment of the invention;  
         [0026]    [0026]FIGS. 2A and 2B schematically show a structure of an circuit unit employing an EMC core supporting member according to a second embodiment of the invention;  
         [0027]    [0027]FIGS. 3A and 3B schematically show a structure of an circuit unit employing an EMC core supporting member according to a third embodiment of the invention;  
         [0028]    [0028]FIG. 4 is a developed view of the EMC core supporting member shown in FIGS. 3A and 3B;  
         [0029]    [0029]FIGS. 5A and 5B show an circuit unit employing a conventional EMC core supporting member; and  
         [0030]    [0030]FIG. 6 shows an appearance of a scope unit for an electronic endoscope system. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0031]    [0031]FIGS. 1A and 1B schematically show a structure of an circuit unit  10  of an electronic endoscope. The circuit unit  10  employs, as a component thereof, an EMC core supporting plate  7  according to a first embodiment of the invention. FIG. 1A is a perspective view showing an inner structure of the circuit unit  10 . FIG. 1B is a cross section taken along line A-A′ of FIG. 1A.  
         [0032]    Similar to the conventional printed circuit board  89  shown in FIGS. 5A and 5B, a printed circuit board  2  shown in FIG. 1A is a circuit board mounting a driving circuit for a CCD, which is provided at a distal end portion of the scope unit, and a signal processing circuit. The printed circuit board  2  is electrically connected to a processor unit through signal cables  3   c  and  4   c , which are connected with connectors  3  and  4  provided on the printed circuit board  2 . The printed circuit board  2  and the CCD are interconnected through a signal cable  5   c , which is connected to a connector  5  mounted on the printed circuit board  2 .  
         [0033]    The EMC core supporting member  7  is a shielding plate formed of a single metal. A shielding section  7   a  of the supporting member  7  expands over an upper surface of the printed circuit board  2  so that it substantially covers the printed circuit board  2 . The supporting member  7  has a U-shaped EMC core supporting portion  7   b , which supports EMC cores  8  and  9 . A signal cable  5   c  is inserted through each of EMC cores  8  and  9  to form a single or a plurality of windings, thereby unintended radiation from the signal cable  5   c , and invasion of noise components therefrom can be prevented.  
         [0034]    As shown in FIG. 1B, the EMC core supporting member  7  is secured on a side surface  1   a  of a housing  1  with screws ls. The side surfaces  1   a  through  1   d  are made of metal, and the EMC core supporting member  7  is electrically connected with the housing  1 . Below a lower surface of the printed circuit board  2 , a shielding plate  6  having an area covering the printed circuit board  2  is arranged. By the side surfaces la through id, the EMC core supporting member  7  and the shielding plate  6 , the entire printed circuit board  2  is shielded. It should be noted that, since the EMC cores  8  and  9  are arranged, on the EMC core supporting member  7 , above a surface thereof opposite to a surface facing the printed circuit board  2 , radiation of noise components from the printed circuit board  2  will not be transmitted to the cable  5   c  which is inserted through the EMC cores  8  and  9 .  
         [0035]    Thus, the EMC core supporting member  7  functions to (a) support the EMC cores  8  and  9 ; (b) shield the printed circuit board  2 ; and (c) shield the EMC cores from the printed circuit board  2 . Because of the above-described configuration, the shield cover  82  as used in the conventional circuit unit  90  shown in FIGS. 5A and 5B is unnecessary.  
         [0036]    Although the EMC core supporting member  7  is secured onto the housing  1  with a screw in the above-described embodiment, it is only an exemplary configuration, and any other securing measure which fixedly and electrically connects the EMC core supporting member  7  with the housing  1  can be employed.  
         [0037]    [0037]FIGS. 2A and 2B schematically shows a structure of an circuit unit  10   b  employing an EMC core supporting member  17  according to a second embodiment. FIG. 2A shows a perspective view of an inner structure of the circuit unit  10   b . FIG. 2B is a cross section of the circuit unit taken along line A-A′ of FIG. 2A.  
         [0038]    As shown in FIG. 2B, the EMC core supporting member  17  is configured such that a U-shaped EMC core supporting element  17   a  is fixed at a substantially central position of the core supporting member  17 . A side portion of the EMC core supporting member  17  is formed to be a connection section  17   b , which is bent at a right angle. The EMC core supporting member  17  is fixed on a side surface la of the housing  1  using screws  11   s . It should be noted that the EMC core supporting member  17  is electrically connected with the side surface la. A bottom surface  17   c  of the EMC core supporting member  17  has an area covering the printed circuit board  2 .  
         [0039]    Similarly to the first embodiment, the side surfaces  1   a  through  1   d  are made of metal, and the EMC core supporting member  17  is electrically connected with the housing  1 . By the side surfaces  1   a - 1   d  of the housing  1 , the EMC core supporting member  17  and the shielding plate  6 , the entire printed circuit board  2  is shielded. Since the EMC cores  8  and  9  are arranged on an upper surface of the EMC core supporting member  17 , while a lower surface faces the printed circuit board  2 , radiation of noise from the printed circuit board  2  will not be transmitted to a cable  5   c  inserted through the EMC cores  8  and  9 .  
         [0040]    It should be noted that the position of the EMC core supporting section  17   a  on the upper surface of the EMC core supporting member  17  is an exemplary arrangement. The position of the EMC core supporting section  17   a  on the upper surface of the EMC core supporting member  17  can be readily modified. Therefore, degree of design freedom when the structure according to the second embodiment is employed in the circuit unit is greater than that employing a conventional structure.  
         [0041]    [0041]FIGS. 3A and 3B show an EMC core supporting member  27  according to a third embodiment of the invention. FIG. 3A shows an inner structure of the circuit unit  10   c , in which the EMC core supporting member  27  is employed. FIG. 3B is a cross section of the EMC core supporting member  27  taken along line A-A′ of FIG. 3A. The EMC core supporting member  27  is formed with an inclined portion  27   d , which is formed by bending a tip end portion of a shielding member  27   c . The inclined portion  27   d  improves shielding effect for the printed circuit board  2 .  
         [0042]    Further, the EMC core supporting member  27  supports, with use of the EMC core supporting section  27   a , a single EMC core  8   a . Similarly to the first and second embodiments, the side surfaces  1   a  through  1   d  are made of metal. By penetrating screws through screw holes (not shown in the drawing) formed on the connection section  27   b , the EMC supporting member  27  is fixed on to a side surface la of the housing  1 , and is electrically connected thereto.  
         [0043]    By the side surfaces  1   a - 1   d  of the housing  1 , the EMC core supporting member  27  and the shielding plate  6 , the entire printed circuit board  2  is shielded.  
         [0044]    [0044]FIG. 4 is a developed view of the EMC core supporting member  27  shown in FIGS. 3A and 3B. In FIG. 4, a broken line indicates a position to be bent. By bending the EMC core supporting member  27  at the broken lines, the inclined portion  27   d  and the connection portion  27   b  are formed as shown in FIGS. 3A and 3B. It should be noted that a surface  27   c  facing the printed circuit board  2  has an area sufficient to cover the printed circuit board  2 .  
         [0045]    It should be noted that the number and size of EMC cores to be employed should be determined depending on the individual device, and the above-described embodiments only show exemplary structures. For example, in the first or second embodiment, the number of EMC cores is not limited to two. A single or more than two EMC cores may be employed. Similarly, in the third embodiment, more than one EMC cores may be employed.  
         [0046]    The present disclosure relates to the subject matter contained in Japanese Patent Application No. 2001-251293, filed on Aug. 22, 2001, which is expressly incorporated herein by reference in its entirety.