Abstract:
The invention provides an electronic device that is environment-friendly and capable of achieving satisfactory noise prevention effect at low cost, and a housing implementing such electronic device. The housing has an electronic circuit disposed therein, and includes a component exposure section in which part of a conductive component disposed in the housing is exposed outward, a plate section made of a conductive material having a predetermined thickness, and spreading at a distance from the component exposure section, and a bridge section with the overall thickness thereof larger than the thickness of the plate section, extending along the component exposure section and electrically connecting the plate section and the conductive component.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an electronic device having an electronic circuit incorporated therein, and to a housing for the same.  
         [0003]     2. Description of the Related Art  
         [0004]     In recent years, as the number of kinds of accessible peripheral devices is growing, note-type personal computers (hereinafter referred to as a note PC, for short) being a type of electronic device with built-in electronic circuits have become more convenient. Accordingly, the kind and number of ports (connectors) used to connect to the peripheral devices are being required to be increased. However, due to restricted mounting space, it is difficult to mount many connectors of various kinds all at once on a note PC itself. Thus, generally, each maker employs a connection configuration such that a separate unit having many connectors of various kinds mounted thereon is provided, and that the separate unit is detachably connected via a dedicated connector to the note PC. In many cases, in view of the wiring on the printed board and of the usability of other units and the note PC, the dedicated connector is mounted on the bottom face in the vicinity of the rear end of the note PC. When the dedicated connector is mounted on such a location, the bottom face of the housing of the note PC must be bored to mount the connector.  
         [0005]     As a material for the bottom face side of the housing of the note PC, there is employed a metal plate-like member for the purposes, such as increasing the strength of a housing and securing the escape path for static electricity. Thus, a boring for mounting the connector is to be positioned around the end of the plate-like member. Also, at the rear end of the note PC, connectors, etc., are protruded outward from the housing, and the shell (metal outer shell section) of the connector is installed in the vicinity of the boring of the plate-like member.  
         [0006]     In a note PC having such a structure, it is known that, when static electricity is applied to the shell of connector by the user&#39;s body coming close to the shell or by other actions, due to the static electricity, there are generated noises which cause the electronic circuit of the note PC to malfunction.  
         [0007]     As a measure against such noises, there have been proposed a technique of plating the inner face of a plastic member constituting the outermost shell of a housing to thereby allow static electricity to escape to the plating film, and a technique of disposing a radiowave absorption sheet inside the housing to thereby prevent noises from entering the electronic circuit (refer to Japanese Patent Laid-Open No. 2001-308574, for example).  
         [0008]     The hitherto proposed techniques, however, can pose problems, such as increasing the cost of note PCs, and hindering weight saving and reduction in thickness which are strongly requested of note PCs. In addition, in recent years, while reduction of adverse environmental effects as introduced when electronic devices are scrapped is strongly requested, the application of plating and radiowave absorption sheet can bring about significant adverse environmental effects.  
         [0009]     These problems are posed not only by note PCs, but generally also by various electronic devices of which a noise countermeasure are requested.  
       SUMMARY OF THE INVENTION  
       [0010]     The present invention has been made in view of the above circumstances and provides an electronic device that is environment-friendly and capable of achieving satisfactory noise prevention effect at low cost, and a housing which can implement such electronic device.  
         [0011]     An electronic device according to the invention includes an electronic circuit; a housing having the electronic circuit disposed therein; and a conductive component disposed in the housing and having part thereof exposed outside the housing, wherein the housing includes a component exposure section in which the conductive component is exposed outward, a plate section made of a conductive material having a predetermined thickness and spreading at a distance from the component exposure section, and a bridge section with the overall thickness thereof larger than the thickness of the plate section, extending along the component exposure section and electrically connecting the plate section and the conductive component.  
         [0012]     Here, the bridge section may be composed of plural overlapping members, or alternatively may be a single member.  
         [0013]     The electronic device according to the invention has a structure in which the overall thickness of the bridge section is larger than the thickness of the plate section. Thus, even when static electricity is applied to a conductive component as typified by a connector component, the static electricity is allowed to rapidly escape through the bridge section to the plate section, thereby suppressing the generation itself of noises to achieve a large noise prevention effect. This structure is based on a hitherto unknown detailed analysis regarding noise generation principle, which will be later described in detail. Due to the simplicity and large effect implemented by the structure, the electronic devices can be small and of low cost. In addition, while avoiding the use of materials bringing about significant adverse environmental effects, such as plating and radiowave absorption sheet, the simple structure of the electronic device according to the invention can be easily realized with a metal plate or the like hardly causing adverse environmental effects.  
         [0014]     The bridge section preferably includes a first section formed of the conductive material integrally with the plate section, and a second section overlapping and contacting the first section. In addition, the bridge section preferably includes a first section formed of the conductive material integrally with the plate section, and a second section overlapping and contacting the first section via a board spring.  
         [0015]     The bridge section having the first and second sections of this type can be easily formed. Also, the configuration in which the second section contacts via a board spring the first section has high contact stability. Consequently, the noise prevention effect can be sufficiently maintained even under severe environments, such as one with vibrations applied.  
         [0016]     A housing according to the invention, having an electronic circuit disposed therein, includes a component exposure section in which part of a conductive component disposed in the housing is exposed outward, a plate section made of a conductive material having a predetermined thickness, and spreading at a distance from the component exposure section, and a bridge section with the overall thickness thereof larger than the thickness of the plate section, extending along the component exposure section and electrically connecting the plate section and the conductive component.  
         [0017]     By employing the housing according to the invention, the above-described electronic device according to the invention can be implemented.  
         [0018]     Regarding the housing of the invention, only its basic configuration will be shown here so that repeated explanation thereof is omitted. Not only the basic configuration but various configurations of the housing corresponding to the above described respective configurations of the electronic device are included in the scope of the invention.  
         [0019]     As described above, according to the invention, the electronic device being environment-friendly and capable of achieving satisfactory noise prevention effect at low cost can be implemented. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  is a diagram showing one embodiment of the invention;  
         [0021]      FIG. 2  is a diagram showing a note PC connected to a separate unit;  
         [0022]      FIG. 3  is a diagram showing the rear side of the note PC;  
         [0023]      FIG. 4  is a first explanatory diagram to describe the internal structure of a main body side housing;  
         [0024]      FIG. 5  is a second explanatory diagram to describe the internal structure of the main body side housing;  
         [0025]      FIG. 6  is a first explanatory diagram to describe the noise generation principle;  
         [0026]      FIG. 7  is a second explanatory diagram to describe the noise generation principle;  
         [0027]      FIG. 8  is a diagram showing a comparative example to which a conventional noise countermeasure is applied;  
         [0028]      FIG. 9  is a first explanatory diagram to describe an operation of the noise countermeasure according to the embodiment of the invention;  
         [0029]      FIG. 10  is a second explanatory diagram to describe the operation of the noise countermeasure according to the embodiment of the invention;  
         [0030]      FIG. 11  is a diagram showing another embodiment of the invention; and  
         [0031]      FIG. 12  is a diagram showing a metal member in which contact stabilization is achieved. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]     Embodiments of the invention will be described below with reference to the drawings.  
         [0033]      FIG. 1  is a diagram showing one embodiment of the invention.  
         [0034]     In  FIG. 1 , a note-type personal computer (note PC)  10  corresponding to one embodiment of the invention is illustrated. The note PC  10  includes a main body  11  and an upper cover  12  that is openable and closable relative to the main body  11 . The upper cover  12  is constructed by incorporating a liquid crystal screen  14  into an upper cover side housing  13 . The main body  11  is constructed by incorporating a pointing device  16  and keys of various kinds  17  into a main body side housing  15 , and incorporating printed boards, semiconductor elements, storage devices, etc. into the interior section of the main body side housing  15 . Also, as described later, various connectors are exposed outward from the rear side of the main body side housing  15 .  
         [0035]     The note PC  10  is detachable relative to a separate unit  20 , and is connected via a dedicated connector  21  to the separate unit  20 .  
         [0036]      FIG. 2  is a diagram showing the note PC  10  connected to the separate unit  20 .  
         [0037]     The separate unit  20  is provided with many connectors of various standards for peripheral device so that various peripheral devices, such as a display, a printer, an external storage device and a communication unit, can be connected thereto. The note PC  10  can access these peripheral devices of various kinds via the separate unit  20 .  
         [0038]     It is desired that the note PC  10  on its own can be connected to some peripheral devices. Thus, various connectors for peripheral device are also provided on the rear side of the note PC  10 .  
         [0039]      FIG. 3  is a diagram showing the rear side of the note PC  10 .  
         [0040]     In the note PC  10 , as the connectors for peripheral device, there are incorporated an output terminal  18   a  of a first kind for external display, an output terminal  18   b  of a second kind for external display, three USB connectors  18   c ,  18   f  and  18   g , a printer port  18   d , and a network connector  18   e , which are exposed outward from the rear side of the main body side housing  15 . In addition, on the rear side of the main body side housing  15 , there is also provided a power source input terminal  19  which supplies the electrical power to the note PC  10 .  
         [0041]     Of various connectors shown here, two kinds of output terminals  18   a  and  18   b  and a printer port  18   d  for external display are exposed outward from the main body side housing  15 ; the outer shell section (shell) of these connectors is made of metal. The connector with such shell corresponds to one example of the conductive component according to the invention; the rear side of the main body side housing  15  corresponds to one example of the component exposure section according to the invention.  
         [0042]     The internal structure of the main body side housing  15  will now be described.  
         [0043]      FIGS. 4 and 5  are explanatory diagrams to describe the internal structure of the main body side housing  15 .  
         [0044]     On the bottom face side of the interior section of the main body side housing  15 , there is incorporated a plate-like member  101  formed by processing a metal plate. The plate-like member  101  has a boring  101   a  so that a connector  21  penetrates. Due to the presence of this boring  101   a , the plate-like member  101  includes a large and wide plate section  101   b  and a slim bottleneck section  101   c . In addition, as shown in  FIG. 5 , on the bottleneck section  101   c , there is overlapped and fastened a slim metal member  102  used for noise countermeasure. The plate section  101   b  of the plate-like member  101  corresponds to one example of the plate section according to the invention; the bottleneck section  101   c  and metal member  102  corresponds to one example of the first and second sections of the bridge section according to the invention, respectively.  
         [0045]     According to the embodiment, as a method for fastening the bottleneck section  101   c  to the metal member  102 , fastening with caulking is employed. According to the invention, however, fastening with screw, etc. can also be alternatively employed. Furthermore, according to the invention, the bottleneck section  101   c  and the metal member  102  may be electrically integrated by joining them with an adhesive, two-sided tape, conductive tape or the like, instead of with fastening, or alternatively may be physically and electrically integrated with welding.  
         [0046]     The metal shells of the connectors shown in  FIG. 3  are electrically connected to both the bottleneck section  101   c  and the metal member  102 .  
         [0047]     Hereinafter, an operation of the noise countermeasure according to the embodiment will be described. Before the description of the operation, firstly a detailed analysis on the noise generation principle and a comparative example to which a conventional noise countermeasure is applied will be described, and then the operation of the noise countermeasure according to the embodiment will be described.  
         [0048]      FIGS. 6 and 7  are explanatory diagrams to describe the noise generation principle. These diagrams are not intended to illustrate the above described embodiment. However, the same reference numerals are applied to elements corresponding to  FIGS. 4 and 5 , and an explanation thereof is omitted.  
         [0049]     In  FIGS. 6 and 7 , there is shown a case where a note PC having no noise countermeasure applied thereto is placed on a steel desk  40 . In addition, a connector shell  18  electrically connected to a bottleneck section  101   c  of a plate-like member  101 , and a semiconductor element  103  and printed board  104  each provided in the interior section of the note PC are also shown. The connector is mounted on the printed board  104 .  
         [0050]     When a finger  30 , etc. of the user comes close to the connector shell  18 , static electricity accumulated in the user&#39;s body can be discharged and applied to the connector shell  18 . The static electricity is apt to flow through the bottleneck section  101   c  to the plate section  101   b . However, the presence of a boring  101   a  makes the impedance of the bottleneck section  101   c  large, thus interrupting the flow of the electrical current.  
         [0051]     According to an analysis by the inventors, etc, it is evident that, at this time, two kinds of noises, i.e. conduction noise traveling through conductive material and radiation noise radiated into the air are generated. As described below, it is clear that, of the two kinds of noises, the malfunction of the semiconductor element  103  is caused by the radiation noise.  
         [0052]     Specifically, when static electricity is discharged from the user&#39;s finger  30 , conduction noise and radiation noise are simultaneously generated. When the energy of conduction noise is compared with that of radiation noise, the energy of the radiation noise is larger than that of the conduction noise because the impedance of the bottleneck section  101   c  is large. Then, the radiation noise travels through a space between the steel desk  40  and plate-like member  101  while being repeatedly reflected, and proceeds through the opening section, gaps, etc. of the plate-like member  101  into the interior section of the note PC. After entering the interior section of the note PC, with a metal pattern  104   a  provided as the signal pattern and power source pattern on the printed board  104  functioning as an antenna, the radiation noise travels to the semiconductor element  103 , thus causing the malfunction of the semiconductor element  103 .  
         [0053]     The noise generation principle like this has hitherto been unknown. Consequently, as a noise countermeasure, an idea that an electronic circuit be covered with a conductive shield has prevailed.  
         [0054]     A comparative example to which a noise countermeasure based on such conventional idea is applied will now be described.  
         [0055]      FIG. 8  is a diagram showing a comparative example to which the conventional noise countermeasure is applied. Also in  FIG. 8 , the same reference numerals are applied to elements corresponding to each of the drawings used in the above descriptions, and an explanation thereof is omitted.  
         [0056]     In the comparative example shown in  FIG. 8 , in addition to the plate-like member  101 , a housing outer shell  105  made of plastic is provided; the inner face of the housing outer shell  105  is plated. The plating film of the housing outer shell  105  electrically contacts the connector shell  18 . Accordingly, static electricity applied to the shell  18  also travels through the plating film of the housing outer shell  105 . Consequently, an effect of reducing radiation noise is achieved.  
         [0057]     However, in the comparative example like this, a large plating film spreading over the inner surface of the housing outer shell  105  is needed, thus hindering downsizing of the note PC and at the same time increasing the cost. Also, the presence of such plating film brings about adverse environmental effects when the note PC is scrapped. Accordingly, it is expected that the application of the structure described in the comparative example into a note PC will soon become impossible.  
         [0058]     In addition to the comparative example shown in  FIG. 8 , there is also an idea that adequate radiowave absorption sheet is spread between the housing outer shell  105  and plate-like member  101  to prevent all noises coming from the outside from entering the plate-like member  101 . However, similarly to the above described comparative example, the presence of such radiowave absorption sheet also hinders downsizing and cost reduction of the note PC, and brings about adverse environmental effects.  
         [0059]     Based on the above described noise generation principle and comparative example, an operation of the noise countermeasure according to the embodiment will be described.  
         [0060]      FIGS. 9 and 10  are explanatory diagrams to describe an operation of the noise countermeasure according to the embodiment. In  FIGS. 9 and 10 , the same reference numerals are applied to elements corresponding to FIGS.  6  to  8 .  
         [0061]     According to the embodiment, on the bottleneck section  101   c  of the plate-like member  101 , there is overlapped and fastened a slim metal member  102 . Also, the connector shell  18  is electrically connected to both the bottleneck section  101   c  and metal member  102 . The overall thickness obtained by combining the bottleneck section  101   c  and metal member  102  is larger than the thickness of the plate section  101   b  of the plate-like member  101 ; the overall impedance obtained by combining the bottleneck section  101   c  and metal member  102  is small. Thus, even when the user&#39;s finger  30  or the like comes close to the shell  18  to discharge static electricity, the electricity flows via each of the bottleneck section  101   c  and metal member  102  to the plate section  101   b , thereby suppressing the noise discharged. Consequently, regarding the printed board  104  and semiconductor element  103  each incorporated in the note PC, the malfunction caused by the metal pattern  104   a  receiving the discharged noise can be substantially prevented. By fabricating the note PC having the structure according to the embodiment to perform a static electricity evaluation, it can be determined that static electricity resistant strength is improved by several kV relative to the conventional art, thus satisfying the level required by the strict international standards.  
         [0062]     Also, according to the embodiment, the noise countermeasure is achieved with a very simple structure having the metal member  102  provided on the bottleneck section  101   c , thereby facilitating downsizing of the note PC, and also contributing to cost reduction. In addition, similarly to the plate-like member  101 , environment-friendly materials can be used for the metal member  102 , which can easily reduce the impact of the note PC on environment.  
         [0063]     Another embodiment of the invention will now be described.  
         [0064]      FIG. 11  is a diagram showing another embodiment of the invention.  
         [0065]     The another embodiment is substantially similar to the above described embodiment except that the metal member for noise countermeasure is disposed in a different location. Accordingly, the difference from the above described embodiment will be mainly described here, and repeated explanation thereof is omitted.  
         [0066]     According to the another embodiment, a slim metal member  107  is fastened along a bottleneck section  101   c  to the lower side of the bottleneck section  101   c , and the note PC is covered with a housing outer shell  106  made of plastic which prevents the metal member  107 , etc. from being exposed.  
         [0067]     The metal member  107  overlaps the bottleneck section  101   c . The metal member  107  and bottleneck section  101   c  constitute another example of the bridge section according to the invention. Also in this embodiment, the overall impedance of the metal member  107  and bottleneck section  101   c  is small, whereby static electricity escapes rapidly through the metal member  107  and bottleneck section  101   c , thus reducing radiation noise.  
         [0068]     In this way, the radiation noise reduction effect is large irrespective of where the metal member is disposed relative to the bottleneck section  101   c . However, when the metal member is loosely fastened to the bottleneck section to thereby make the contact unstable, the reduction effect is also made unstable. Therefore, it is desired that the contact between the bottleneck section and metal member is made stable.  
         [0069]      FIG. 12  is a diagram showing a metal member in which contact stabilization is achieved.  
         [0070]     The metal member  108  shown in  FIG. 12 , which is used instead of the metal member  102  shown in  FIGS. 5, 9 , and  10 , or the metal member  107  shown in  FIG. 11 , has a structure formed by providing a board spring section  108   b  at both ends of a main body  108   a . The board spring section  108   b  like this is formed by bending at both ends a metal board out of which the metal member  108  is made, and then forming notches to divide the metal board into plural sections. The metal member  108  having such structure strongly contacts the bottleneck section with the force of the board spring section  108   b , and at the same time has large contact stability. Accordingly, the radiation noise reduction effect as described above can be stably utilized for long periods even under severe environments, such as one with vibrations applied.  
         [0071]     In the above descriptions, as one example of the bridge section according to the invention, there is shown one formed by disposing the slim metal member on the bottleneck section of the plate-like member. The bridge section according to the invention, however, may be one fabricated with a thicker material than the plate section separately from the plate section and attached to the plate section, or alternatively may be one obtained by processing a metal board in which the vicinity of the bridge section is originally thicker than the other sections of the metal board so that the bridge section is formed integrally with the plate section.  
         [0072]     Also, in the above descriptions, as one example of the electronic device according to the invention, the note PC is shown. The electronic device according to the invention, however, may be a computer other than note-type one, or alternatively may be an electronic device other than a computer, such as an electronic measurement device.