Abstract:
Provided is an electronic controller which enables visual identification of a portion applied with a small amount of a sealing material, which has a high possibility of air leakage from an area in which a joint is to be established. The electronic controller includes: an electronic circuit board; and a casing including a cover ( 1 ), a base ( 4 ), and a lid sealed with a sealing material ( 20 ) applied to surfaces thereof at which the cover ( 1 ), the base ( 4 ), and the lid are to be joined together. An area in which the cover ( 1 ), the base ( 4 ), and the lid are to be joined together is provided with a space ( 16 ) thereto for enabling an application state of the sealing material ( 20 ) to be observed with a naked eye.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electronic controller which includes electronic components mounted on an electronic circuit board housed within a casing. 
     2. Description of the Related Art 
     An electronic controller, which is used for controlling a vehicle or the like, includes an electronic circuit board, a plurality of electronic components, and a casing. On the electronic circuit board, connectors for electrical connection to the exterior are provided. The plurality of electronic components are mounted on the electronic circuit board. The casing is made of a resin or a metal. The electronic circuit board is housed in the casing for protection of the electronic components. 
     Among various types of electronic controller, an electronic controller provided in an engine room or directly mounted on an engine has a water-proof structure in view of a possibility of getting wet with water. As an example of the electronic controller described above, there exists an electronic controller disclosed in Japanese Patent Application Laid-open No. 2003-258454 (FIGS. 4 and 5). 
     The electronic controller described in Japanese Patent Application cited above has the following structure. A casing including vertically separated members, that is, a base and a cover, is used to interpose an electronic circuit board on which a connector is provided. A gap between a peripheral wall end surface of the base and a flange portion of the cover is sealed with a water-proof sealing material. 
     A sealing structure at surfaces, at which the base and the connector, and the cover and the connector are to be respectively jointed together, is as follows. A groove is provided on the connector. A projecting portion is provided on the cover at a position corresponding to the groove, whereas another projecting portion is provided on the base. A water-proof sealing material is provided in the groove of the connector. In this manner, the gaps between the cover and the connector and between the base and the connector are sealed. 
     In the electronic controller having the water-proof structure as described in Japanese Patent Application Laid-open No. 2003-258454 cited above, it is necessary to check a water-proofing property thereof by an airtightness test so as to ensure the water-proofing property after the assembly of the electronic controller. 
     In a case of electronic controllers using an adhesive or a liquid packing as a sealing material, when an electronic controller which does not meet a predetermined standard because of a small application amount of the sealing material is found in the airtightness test for the casing of the electronic controller, it is necessary to additionally apply the sealing material from the exterior to an area of the casing, in which a joint is to be established, and to conduct the airtightness test again. 
     In the case of the electronic controller described above, however, the application amount of the sealing material on the area of the casing, in which a joint is to be established, cannot be easily checked. Therefore, it is difficult to identify a portion from which air leaks, specifically, a portion which requires to be additionally applied with the sealing material. 
     If, for example, complicated tasks such as immersing the electronic controller into a tank storing water therein and feeding air into the electronic controller to identify the air leakage portion are performed, the air leakage portion can be identified. However, conducting such tasks in a fabrication line for the electronic controllers is not practical in view of a line space, capital investment, and fabrication cost. 
     As described above, the conventional electronic controllers have had a problem in that it is difficult to identify a portion with a small amount of the sealing material, which has a high possibility of air leakage, and to additionally apply the sealing material only to the identified portion at the location of assembly. 
     As countermeasures against the aforementioned problem, it is possible to conceive of additionally applying the sealing material over the entire periphery from the exterior of the casing of the electronic controller. In this case, however, there arises another problem in that the amount of the sealing material to be used disadvantageously increases, thereby increasing the cost of the electronic controller. 
     SUMMARY OF THE INVENTION 
     The present invention has been made to solve the problems described above, and therefore, has an object to provide an electronic controller which enables visual identification of a portion applied with a small amount of a sealing material, which has a high possibility of air leakage from an area in which a joint is to be established, so as to reduce a reject ratio in an airtightness test and thus improve the efficiency of assembly operation by additionally applying the sealing material to the visually identified portion before the airtightness test is conducted. 
     Further, the present invention has another object to provide an electronic controller which enables the use of an appropriate amount of the sealing material and thus eliminates an unnecessary use of the sealing material by applying the sealing material only to the portion applied with the small amount of the sealing material when the sealing material is to be additionally applied. 
     An electronic controller according to the present invention includes: an electronic circuit board having electronic components mounted thereon; and a casing for housing the electronic circuit board therein, the casing including a plurality of casing members sealed with a sealing material applied to surfaces at which the plurality of casing members are to be joined together, in which an area in which the plurality of casing members are to be joined together is provided with a space thereto for enabling an application state of the sealing material to be observed with a naked eye from exterior in a state in which the plurality of casing members are joined together. 
     According to the electronic controller of the present invention, the space enabling the application state of the sealing material to be observed with the naked eye from the exterior, in a state in which the casing members are joined together, is provided to the area in which the casing members are to be joined together. Therefore, the portion applied with the small amount of the sealing material, which has the high possibility of air leakage from the area in which the casing members are to be joined together can be visually identified. As a result, by additionally applying the sealing material before the airtightness test is conducted, the reject ratio in the test can be reduced and the efficiency of assembly operation can be improved. 
     Further, by applying the sealing material only to the portion applied with the small amount of sealing material when the sealing material is to be additionally applied, the use of the appropriate amount of the sealing material can be attained, and thus the unnecessary use of the sealing material can be eliminated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is an exploded perspective view schematically illustrating a structure of an electronic controller according to Embodiment 1 of the present invention; 
         FIG. 2A  is a sectional view of a principal part of a cover and a base illustrated in  FIG. 1  before the cover and the base are joined together; 
         FIG. 2B  is a sectional view of the principal part illustrated in  FIG. 1  after the cover and the base are joined together; 
         FIG. 2C  is a sectional view of the principal part of the cover and the base, illustrating a variation of an area in which the cover and the base are to be joined together; 
         FIG. 3  is a perspective view of one of claws illustrated in  FIG. 1 ; 
         FIG. 4A  is a sectional view of a principal part of a cover and a base of an electronic controller according to Embodiment 2 of the present invention before the cover and the base are joined together; 
         FIG. 4B  is a sectional view of the principal part of the cover and the base after the cover and the base are joined together; 
         FIG. 5  is an exploded sectional view schematically illustrating a structure of an electronic controller according to Embodiment 3 of the present invention; 
         FIG. 6A  is a sectional view of a principal part of a casing main body and a lid illustrated in  FIG. 5  before the casing main body and the lid are joined together; and 
         FIG. 6B  is a sectional view of the principal part of the casing main body and the lid after the casing main body and the lid are joined together. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, an electronic controller according to embodiments of the present invention is described with reference to the drawings. In the drawings, the same or equivalent members or portions are denoted by the same reference numeral for description. 
     Embodiment 1 
       FIG. 1  is an exploded perspective view schematically illustrating a structure of an electronic controller according to Embodiment 1 of the present invention. 
     The electronic controller includes an electronic circuit board  2  having electronic components  5  mounted thereon, and a casing which houses the electronic circuit board  2  therein. 
     The casing includes a base  4 , a cover  1 , and a lid  30 . The base  4  and the cover  1  interpose the electronic circuit board  2  from both sides to cover the electronic circuit board  2 . The lid  30  supports connectors  3 , each being electrically connected to the electronic circuit board  2 , and closes an opening portion  36  formed by the base  4  and the cover  1 . 
     Note that, the lid  30  and the connectors  3  may be formed as one component instead of being formed as separate members. 
     In this embodiment, casing members constituting the casing are the base  4 , the cover  1 , and the lid  30 . 
     As a material of the cover  1 , the base  4 , and the lid  30 , a metal having a high thermal conductivity, such as aluminum, is desirable in view of heat-radiation performance. However, when the heat-radiation performance is not needed, other materials may be used. 
     Three sides of the base  4  having a rectangular shape and three sides of the cover  1  are joined together by using a sealing material  20 . A lower end of the lid  30  is joined to one side of the base  4  having the rectangular shape by using the sealing material  20 . An upper end of the lid  30  is joined to an inner peripheral portion of the opening portion  36  of the cover  1  by using the sealing material  20 . The opening portion  36  has a trapezoidal shape. 
     The sealing material  20  is applied to grooves  10  and  11 . The groove  10  is formed along four sides of the base  4 , whereas the groove  11  is formed along upper three end surfaces of the lid  30 . 
       FIG. 2A  is a sectional view of a principal part of the cover  1  and the base  4  illustrated in  FIG. 1  before the cover  1  and the base  4  are joined together, whereas  FIG. 2B  is a sectional view of the principal part of the cover  1  and the base  4  illustrated in  FIG. 1  after the cover  1  and the base  4  are joined together. 
     A projection  12  is formed over the entirety of a lower end of the cover  1 . The projection  12  is formed so as to be bent at a base thereof. A width W 1  of the projection  12  is smaller than a width W 2  of the groove  10 . 
     When the cover  1  and the base  4  are to be joined together, an inner wall surface  39  of the projection  12  comes into surface contact with an inner wall surface  34  of the groove  10  of the base  4 . Then, the projection  12  is lowered in this state. In this manner, the projection  12  presses and flattens the sealing material  20  applied to the groove  10 . 
     As illustrated in  FIG. 2B , when the cover  1  and the base  4  are joined together, the sealing material  20  is pushed to flow into a space  16  formed by a difference between the width W 2  of the groove  10  and the width W 1  of the projection  12  of the cover  1 . The space  16  is a clearance formed in an area in which the cover  1  and the base  4  are to be joined together when the projection  12  is inserted into the groove  10 . 
     Therefore, through the space  16  formed in the area in which the cover  1  and the base  4  are to be joined together, an application state of the sealing material  20  can be checked with the naked eye in a state in which the cover  1  and the base  4  are joined together. 
     In this example, the space  16  enabling the application state of the sealing material  20  to be checked with the naked eye from the exterior is provided so as to extend horizontally in parallel to the base  4 . 
     Therefore, the application state of the sealing material  20  can be easily checked in a comfortable posture without moving the casing. Accordingly, high workability during the checking is provided. 
     Further, the projection  12  of the cover  1  is lowered while the inner wall surface  39  thereof is held in surface contact with the inner wall surface  34  of the groove  10 . Therefore, the sealing material  20  does not flow into the interior of the casing and stays in the space  16  enabling the application state of the sealing material  20  to be checked from the exterior. Accordingly, a portion with an insufficient amount of the sealing material  20  can be easily identified. 
     The space  16  formed in the area in which the base  4  and the cover  1  are to be joined together has an opening width for additionally applying the sealing material  20  from the exterior and functions as a space for storing the sealing material  20  therein. Therefore, when the application amount of the sealing material  20  is small, additional application of the sealing material  20  can be easily performed through the space  16 . 
     The opening width of the space  16  is larger than a diameter of a nozzle  50  of sealing-material injection means for additionally applying the sealing material  20  from the exterior. The additional application of the sealing material  20  is performed while the nozzle  50  is oriented toward the groove  10  through the space  16 . 
       FIG. 2C  is a sectional view illustrating an example where a space  16 A for checking the application state of the sealing material  20  is provided so as to extend vertically. 
     In this example, a protruding portion  38  which extends horizontally is formed on the lower end of the cover  1 . The space  16 A is formed between the protruding portion  38  and the base  4 . 
     When the space  16 A is provided vertically with respect to the base  4 , as compared with the case where the space  16  is provided horizontally, a space for storing the sealing material  20  is secured in the vertical direction, although it is necessary to move the casing to check the surfaces at which the cover  1  and the base  4  are joined together in order to check the application state of the sealing material  20 . Therefore, the outer dimension of the casing can be designed smaller. Accordingly, the example with the space  16 A is advantageous in terms of reduction in size. 
     Note that, a color of the sealing material  20  may be set different from that of the cover  1 , the base  4 , and the lid  30 , serving as the casing members constituting the casing, so that the application state of the sealing material  20  is more easily checked. 
     Further, a colorless and transparent material may be used for the cover  1  so that the application state of the sealing material  20  is more easily checked in the areas in which the cover  1  and each of the base  4  and the lid  30  are to be joined together. 
     In this case, the space in the areas in which the cover  1  and each of the base  4  and the lid  30  are to be joined together may be omitted. 
       FIG. 3  is a perspective view illustrating one of claws  13  provided to the cover  1 . 
     The claws  13  are formed on the lower edge of the cover  1  at three positions. 
     A hole  14  is formed at a base of each of the claws  13 . A locking portion  37  is formed on the base  4  so as to correspond to the claw  13 . The claw  13  is elastically locked to the locking portion  37 . In this manner, the cover  1 , the base  4 , and the lid  30  are prevented from being moved relative to each other until the sealing material  20  is cured. 
     The hole  14  formed at the base is formed simultaneously with formation of the claw  13 . Through the hole  14 , the application state of the sealing material  20  can be checked, as in the case of the surfaces of the cover  1  and the base  4  at which the cover  1  and the base  4  are to be joined together except for the claws  13 . 
     The hole  14  has an opening width for additional application of the sealing material  20  and is also used as a space for storing the sealing material  20  for the additional application as in the case of the space  16  formed in the area in which the cover  1  and the base  4  are to be joined together except for the claws  13 . 
     Note that, a height of the sealing material  20  in the hole  14  may be used as a criterion for determining the application amount of the sealing material  20 . 
     Therefore, even in portions with the claw  13 , the application state of the sealing material  20  can be checked. Thus, the same effect as that of portions without the claws  13  can be obtained. 
     Moreover, the hole  14  provided at the base of the claw  13  has the opening width enabling the additional application of the sealing material  20 . Therefore, workability during additional application of the sealing material  20  is improved. 
     Note that, the area in which the cover  1  and the lid  30  are to be joined together has the same structure as that of the area in which the cover  1  and the base  4  are to be joined together. Thus, the structure provides such effects as enabling the application state of the sealing material  20  to be checked with the naked eye, through the space formed in the area in which the cover  1  and the lid  30  are to be joined, in the state in which the cover  1  and the lid  30  are joined together. 
     Embodiment 2 
       FIG. 4A  is a sectional view of a principal part of the cover  1  and the base  4  of an electronic controller according to Embodiment 2 of the present invention before the cover  1  and the base  4  are joined together, whereas  FIG. 4B  is a sectional view of the principal part of the cover  1  and the base  4  after the cover  1  and the base  4  are joined together. 
     In this embodiment, a jetty  18  is provided to the cover  1  so as to be formed on an inner side of a projection  12 A and be opposed to the projection  12 A. A dimension of the jetty  18  toward the base  4  is longer than a dimension of the projection  12 A toward the base  4 . 
     The remaining configuration is the same as that of the electronic controller of Embodiment 1. 
     In this embodiment, before the projection  12 A of the cover  1  presses and flattens the sealing material  20 , an inner wall surface  40  of the jetty  18  comes into contact with an inner wall surface  35  of the base  4 , and then the jetty  18  is lowered while blocking an inflow path of the sealing material  20  into the interior of the casing. Therefore, the sealing material  20  is prevented from entering the interior of the casing. 
     Whereas two surfaces of the projection  12  are covered with the sealing material  20  in Embodiment 1 as illustrated in  FIG. 2B , all the surfaces of the projection  12 A are covered with the sealing material  20  in this Embodiment 2. Therefore, a length over which the projection  12 A is in contact with the sealing material  20  becomes correspondingly long as compared with that in Embodiment 1. Accordingly, higher adhesion strength and sealability between the cover  1  and the base  4  are provided. 
     The remaining functions and effects are the same as those of the electronic controller according to Embodiment 1. 
     Note that, the area in which the cover  1  and the lid  30  are to be joined together has the same structure as that of the area in which the cover  1  and the base  4  are to be joined together. Thus, the structure provides such effects as enabling the application state of the sealing material  20  to be checked with the naked eye, through the space formed in the area in which the cover  1  and the lid  30  are to be joined together, in the state in which the cover  1  and the lid  30  are joined together. 
     Embodiment 3 
       FIG. 5  is an exploded sectional view schematically illustrating a structure of an electronic controller according to Embodiment 3 of the present invention.  FIG. 6A  is a sectional view of a principal part of a casing main body  7  and a lid  30 A illustrated in  FIG. 5  before the casing main body  7  and the lid  30 A are joined together, whereas  FIG. 6B  is a sectional view of the principal part of the casing main body  7  and the lid  30 A after the casing main body  7  and the lid  30 A are joined together. 
     The electronic controller according to Embodiment 3 includes the casing main body  7  and the lid  30 A. The casing main body  7  is a casing member which houses an electronic circuit board  2 A therein. The lid  30 A is a casing member which supports connectors  3 A electrically connected to the electronic circuit board  2 A and closes an opening portion  36 A of the casing main body  7 . 
     Note that, the lid  30  and the connectors  3 A may be formed as one component instead of being formed as separate members. 
     A groove  10 A is formed on the casing main body  7  so as to surround the entire periphery of the opening portion  36 A. The projection  12 A is formed on the lid  30 A so as to be opposed to the groove  10 A, which is to be applied with a sealing material  20 A. 
     In this embodiment, when the lid  30 A and the casing main body  7  are to be joined together, an inner wall surface  39 A of the projection  12 A is lowered while being held in surface contact with an outer peripheral end surface  42  of the casing main body  7 . In this manner, the projection  12 A presses and flattens the sealing material  20 A applied to the groove  10 A. 
     As illustrated in  FIG. 6B , a space  16 B is provided in an area in which the lid  30 A and the casing main body  7  are to be joined together. The sealing material  20 A is pressed to flow into the space  16 B. Through the space  16 B, an application state of the sealing material  20 A can be checked when the lid  30 A and the casing main body  7  are joined together. 
     The space  16 B for checking the state of the application of the sealing material  20 A to the groove  10 A of the casing main body  7  has an opening width for additionally applying the sealing material  20 A from the exterior, and functions as a space for storing the sealing material  20 A therein. Therefore, when the application amount of the sealing material  20 A is small, additional application of the sealing material  20 A can be easily performed through the space  16 B. 
     The opening width of the space  16 B is larger than the diameter of the nozzle  50  of the sealing-material injection means for additionally applying the sealing material from the exterior. 
     Note that, the groove  10  is formed on the base  4  and the projection  12  is formed on the cover  1  in Embodiments 1 and 2 described above, but the groove may be formed on the cover and the projection may be formed on the base. 
     Further, the groove  10 A is formed on the casing main body  7  and the projection  12 A is formed on the lid  30 A in Embodiment 3 described above, but the groove may be formed on the lid and the projection may be formed on the casing main body. 
     Still further, the three casing members are used to constitute the casing in Embodiments 1 and 2, and the two casing members are used to constitute the casing in Embodiment 3. However, it is apparent that four or more casing members may be used to constitute the casing.