Patent Publication Number: US-2007124008-A1

Title: Design support system and design support method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2005-347111, filed Nov. 30, 2005, the entire contents of which are incorporated herein by reference.  
     BACKGROUND  
      1. Field  
      One embodiment of the invention relates to a design support system and a design support method which check whether or not electromagnetic radiation may leak from a housing.  
      2. Description of the Related Art  
      The amount of electromagnetic radiation emanating from electronic instruments is restricted. To prevent the amount of electromagnetic radiation emanating from an electronic instrument from exceeding the range stipulated by regulations, electromagnetic field analysis is started at the stage of product design to determine where in the product electromagnetic radiation is likely to leak and so cause trouble (Jpn. Pat Appln. KOKAI Publication No. 2002-149720).  
      However, electromagnetic field analysis requires a very long time. This delays taking appropriate action for parts from which electromagnetic radiation is likely to leak, increasing the time required to design the product. However, to reduce the time required to design the product, it is desirable to easily determine where electromagnetic radiation is likely to leak. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
      A general architecture that implements the various feature of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention.  
       FIG. 1  is an exemplary block diagram showing the general configuration of an EMC design support system according to an embodiment of the present invention;  
       FIG. 2  is an exemplary diagram showing the structure of CAD data according to the embodiment of the present invention;  
       FIG. 3  is an exemplary diagram of part shapes expressed on the basis of CAD data according to the embodiment of the present invention;  
       FIG. 4  is an exemplary diagram showing the correspondence between a PRT file and material information;  
       FIG. 5  is an exemplary diagram showing an example in which conductive-plating application range information is incorporated into the PRT file;  
       FIG. 6  is an exemplary flowchart showing the procedure of a process executed by the EMC design support system according to the embodiment of the present invention;  
       FIG. 7  is an exemplary diagram showing the configuration of a circuit board, a housing base, and a housing cover expressed on the basis of CAD data;  
       FIG. 8  is an exemplary diagram showing connections with a reference ground on the circuit board; and  
       FIG. 9  is an exemplary table showing determinations made by the EMC design support system according to the embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION  
      Various embodiments according to the invention will be described hereinafter with reference to the accompanying drawings. In general, according to one embodiment of the invention, a design support system which supports verification of design of a product, includes, check target setting unit which sets a part shape model to be a check target, from a plurality of part shape models for the product including a housing, material information acquiring unit which acquires information on a material for each of the plurality of part shape models, reference ground setting unit which sets one of the plurality of part shape models to be a reference ground, extracting/measuring unit which extracts conductive paths from the part shape models ranging from the part shape model set to be the check target to the part shape model serving as the reference ground, on the basis of the information on the material for each of the part models, and measuring the lengths of the extracted paths, and detecting unit which detects where electromagnetic radiation of a level equal to or greater than a criterion value is likely to leak outside the housing.  
       FIG. 1  is a block diagram showing the configuration of an electromagnetic compatibility (EMC) design support system.  
      An EMC design support system  100  has a computer-aided design (CAD) data acquiring section  101 , a material information acquiring section  102 , and a conductive-plating application range acquiring section  103  which acquire various items of data (information) from a database  10 .  
      The CAD data acquiring section  101  acquires CAD data  11  from the database  10 . The material information acquiring means  102  acquires material information  12  from the database  10 . The conductive-plating application range acquiring section  103  acquires conductive-plating application range information  13  from the database  10 .  
      The CAD data  11  acquired by the CAD data acquiring section  101  is formed of a plurality of small assembled files. For example, as shown in  FIG. 2 , the CAD data  11  indicates a tree structure. Specifically, BASE.ASM is composed of an assembly of three files (part shape models), BRACKET.PRT, BUSHING.PRT, and RING.PRT. Files for individual parts are hereinafter referred to as PRT files. A collection of PRT files is hereinafter referred to as an ASM file. However, an ASM file may contain a plurality of ASM files.  
       FIG. 3A  shows a part shape expressed on the basis of BASE.ASM.  FIG. 3B  shows a part shape expressed on the basis of BRACKET.ASM.  FIG. 3C  shows a part shape expressed on the basis of BUSHING.ASM.  FIG. 3D  shows a part shape expressed on the basis of RING.ASM.  
      The material information acquiring section  102  acquires the material information  12  from the database  10 . The PRT file contains data on the shape of a part but may not contain the material information. To execute checks on the basis of EMC, it is important to distinguish metal from nonmetal. The database  10  stores the material information for each PRT file. If possible, physical property values such as conductivity are added to the database  10 . The material information  12  acquired by the material information acquiring section  102  is associated with each PRT file for the CAD data  11 , as shown in  FIG. 4 .  
      The conductive-plating application range acquiring section  103  acquires the conductive-plating application range information  13  from the database  10 . In designing a digital instrument, the interior of a nonconductive housing may be conductively plated in order to hinder noise from a circuit board from leaking outside the instrument. In connection with EMC, the range of application of conductive plating is important. If possible, physical property values such as the conductivity of the conductive plating are added to the conductive-plating application range information  13 .  
      A conductive-plating range synthesizing section  104  incorporates conductive-plating application information in the conductive-plating application range information  13  into the PRT file in the CAD data acquired by the CAD data acquiring section  101 .  FIG. 5  shows an example in which the conductive-plating application range information is incorporated into the PRT file. In the example shown in  FIG. 5 , the instrument is conductively plated except for an area in which heat exhaust apertures  201  are formed.  
      A reference ground setting section  105  uses a connection path extracting/measuring section  108  to set a part or area serving as a reference ground for a housing frame. The part or area serving as the reference ground for the housing frame is set in accordance with a user&#39;s specification. For example, the reference ground setting section  105  displays, on a display device  121 , a structure corresponding to the ASM file. During display, the reference ground setting section  105  displays conductive parts and a conductive-plating application range in a special manner. The user selects from the special display portions via an input device  122  such as a mouse to specify the part or area serving as the reference ground. A plurality of parts and areas serving as reference grounds can be selected. Alternatively, it is possible to select from the ASM files or PRT files. If only a portion of a part is conductively plated, only that conductive-plating application area can be specified as a reference ground.  
      A check target setting section  106  sets a part to be checked in the connection path extracting/measuring section  108 . The part or area to be checked is set in accordance with the user&#39;s specification. For example, the check target setting section  106  displays the structure corresponding to an ASM file, on the display device  121 . Then, in response to the user&#39;s selection via the input device  122  such as a mouse, the check target setting section  106  specifies the part or area to be checked. A plurality of parts or areas serving as reference grounds can be selected. Alternatively, it is possible to select from the ASM files or PRT files.  
      An extraction distance setting section  107  sets, in the connection path extracting/measuring section  108 , an extraction distance Lmax input by the user via the input device  122  such as a keyboard.  
      The connection path extracting/measuring section  108  extracts, from the check a target part or area set by the check target setting section  106 , all “conductive” paths to the reference ground part or area set by the reference ground setting section  105 , within the range of the extraction distance Lmax set by the extraction distance setting section  107 . The connection path extracting/measuring section  108  measures the length of each of the extracted paths. The connection path extracting/measuring section  108  supplies the extracted paths and the path lengths to a determining section  110 .  
      A connection determination distance setting section  109  sets, in the determining section  110 , a connection determination distance L input by the user via the input device  122  such as a keyboard.  
      The determining section  110  determines whether or not electromagnetic radiation of a level equal to or higher than a criterion value is likely to leak at the measured distance of each path supplied by the connection path extracting/measuring section  108 , on the basis of the connection determination distance L set by the connection determination distance setting section  109 . The determining section  110  supplies determinations to a result output section  111 . A greater connection distance is likely to increase the amount of electromagnetic radiation generated. Thus, if the path length determined by the connection path extracting/measuring section  108  is equal to or greater than the connection determination distance L, the determining section  110  determines that electromagnetic radiation of the level equal to or higher than a criterion value is likely to leak.  
      The result output section  111  displays, on the display device, the determinations supplied by the determining section  110 .  
      Now, an actual procedure will be described with reference to the flowchart in  FIG. 6 .  
      First, the CAD data acquiring section  101  acquires mechanical CAD data  11  containing the check target part or area from the database  10  (block S 11 ). For example, as shown in  FIG. 7 , CAD data  11  is acquired which indicates that a circuit board  210  that generates electromagnetic radiation is installed inside a housing base  221  and a housing cover  222 .  
      Then, the material information acquiring section  102  acquires the material information  12  from the database  10  (block S 12 ). The housing base  221  and the housing cover  222  are plastic parts (nonconductive parts).  
      The conductive-plating application acquiring section  103  acquires the conductive-plating application range information  13  from the database  10  (block S 13 ). Since the housing base  221  and housing cover  222  are partly conductively plated, the conductive-plating application acquiring section  103  acquires the conductive-plating application range information  13  corresponding to the housing base  221  and housing cover  222 .  
      The conductive-plating range synthesizing section  104  then incorporates conductive-plating application information in the conductive-plating application range information  13  into a PRT file in the CAD data acquired by the CAD data acquiring section  101  (block S 14 ).  
      The reference ground setting section  105  then sets, in the connection path extracting/measuring section  108 , a part or area serving as a reference ground (block S 15 ). In this case, the conductive plating applied to the parts of the housing  221  and housing cover  222  is a reference ground.  
      The check target setting section  106  then sets a check target part or area in the connection path extracting/measuring section  108  (block S 16 ). In the present embodiment, the check target is set to be the circuit board  210 .  
      The extraction distance setting section  107  then sets, in the connection path extracting/measuring section  108 , an extraction distance Lmax input by the user via the input device  122  (block S 17 ). This processing may be executed at any time before the processing in the next block S 18  is executed.  
      The connection path extracting/measuring section  108  then extracts, from the check target part or area set by the check target setting section  106 , all “conductive” paths to the reference ground part or area set by the reference ground setting section  105  within the range of the extraction distance Lmax set by the extraction distance setting section  107 . The connection path extracting/measuring section  108  measures the length of each of the extracted paths (block S 18 ). The connection path extracting/measuring section  108  supplies the extracted paths and the path lengths to the determining section  110 . As shown in  FIG. 8 , connection positions C 1 , C 2 , C 3 , C 7 , C 8 , and C 9  on the circuit board  210  are connected to the housing base  221  and the housing cover  222 . Connection positions C 4  and C 6  on the circuit board  210  are connected to the housing base  221 . A connection position C 5  on the circuit board  210  is connected to the housing cover  222 .  
      The connection determination distance setting section  109  sets, in the connection path extracting/measuring section  108 , a connection determination distance L input by the user via the input device  122  (block S 19 ). This processing may be executed at any time before the processing in the next block S 20  is executed.  
      The determining section  110  selects one of the paths extracted by the connection path extracting/measuring section  108 . The determining section  110  determines whether or not the measured length of the selected path is less than the connection determination distance L set by the connection determination distance setting section  109  (block S 20 ).  
      If the measured length is less than the connection determination distance L (Yes in block S 20 ), the determining section  110  assumes that the amount of electromagnetic radiation likely to leak from the selected path to the outside of the housings  221  and  222  is less than the criterion value. The determining section  110  thus determines that the selected path is OK (block S 21 ). If the measured length is equal to or greater than the connection determination distance L (No in block S 20 ), the determining section  110  assumes that the amount of electromagnetic radiation likely to leak from the selected path to the outside of the housings  221  and  222  is equal to or greater than the criterion value. The determining section  110  thus determines that the selected path is NG (block S 22 ).  
      After the processing in block S 21  or S 22 , the determining section  110  determines whether or not any of the paths extracted by the connection path extracting/measuring section  108  has failed to be subjected to determination (block S 23 ). If any path has failed to be subjected to determination (Yes in block S 23 ), the determining section  110  selects that path having failed to be subjected to determination and executes the processing in block S 20 .  
      If all the paths have been subjected to determination (No in block S 23 ), the result output section  111  shows, on the display device  121 , the determinations for all the paths extracted by the connection path extracting/measuring section  108  (block S 24 ).  FIG. 9  shows the determinations. As shown in  FIG. 8 , when displayed, the connections may be classified into those between the substrate  210  and the housing base  221  and housing cover  222 , those between the substrate  210  and the housing base  221 , and those between the housing cover  222  and the substrate  210 .  
      The housing can be easily checked for areas of possible leakage of electromagnetic radiation by extracting the frame ground connection structure at a time and determining whether or not electromagnetic radiation of a level equal to or greater than the criterion value is likely to leak on the basis of the connection path length. Parts that are likely to cause trouble can be mechanically extracted. This makes it possible to quickly take measures against the leakage of electromagnetic radiation and to reduce the time required for product design.  
      Preferably, the present support system further has a function for displaying conductive paths. Preferably, the present support system further has a function for approximating a resistance value from the physical values of the part located between the connection paths. Preferably, the present support system further has a function for creating a report on check results as shown in  FIG. 9 . Preferably, the present support system further has a function for checking whether or not the connection interval is valid for the frequencies of signals used in the instrument.  
      A computer program implements all of the processing required to check where in a housing electromagnetic radiation is likely to leak according to the present invention. Accordingly, effects similar to those of the present embodiment can be easily realized simply by installing this computer program in a normal computer through a computer readable storage medium. The computer program can be executed not only on a personal computer but also on various electronic instruments containing processors.  
      While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.