Abstract:
The purpose of the present invention is to provide a control unit whereby the quantity of a seal material to be used can be reduced, while ensuring waterproof performance. This electronic control device is provided with: a housing, wherein a plurality of members are bonded, and a peripheral end portion thereof is configured from a plurality of sides; a circuit board housed in the housing; and seal structures that are disposed along the sides at the peripheral end portion. A seal material is provided to the seal structures such that the members are connected to each other. The seal structures disposed on one side of the peripheral end portion are configured such that each of seal cross sectional areas at end portions of the side is smaller than a seal cross sectional area at a center portion of the side.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a seal structure of an electronic control device which is mounted on an automobile or the like. 
       BACKGROUND ART 
       [0002]    Recently, improvement in fuel efficiency of automobiles, engine room narrowing, and cost reduction of vehicles are advancing in an automobile industry. Electronic control units for controlling engines, transmissions, etc are provided in the vehicle and further reduction in size, weight, and cost are also required in these electronic control units. 
         [0003]    Meanwhile, the electronic control units tend to be directly attached to a vehicle body side in an inside of the engine room from an inside of a vehicle passenger compartment, and further to the engines, the transmissions, or the like to be controlled. Therefore, a housing coping with a mounting environment, such as a waterproof structure, a corrosion resistant structure, and coping with high temperature is required in the electronic control units. Accordingly, the electronic control units waterproof an electronic circuit board by interposing a seal material on a peripheral portion or the like of an exterior member forming the housing. A silicone based adhesive and a rubber packing are common as the seal material. However, the silicone based adhesives or the rubber packing is a material with high cost, and wide area for sealing is required. Accordingly, an example of a method for promoting compactness, weight reduction and cost reduction of the electronic control units, includes reduction of the seal material. 
         [0004]    As a background art of the present invention, there is a JP-A-2013-69735 (PTL 1). A seal structure of an electronic control device that includes a housing seal portion which is provided in an endless annular shape over the entirety of the periphery of a mating surface portion between a peripheral portion of an upper surface side of a case and a peripheral portion of a lower surface side of a cover, and a connector seal portion which is provided in an endless annular shape over the entirety of the periphery of a joining surface portion between an outer peripheral surface of a connector and an inner peripheral surface of a window portion of the housing (case and cover) is described in paragraphs 0021 to 0027 of PTL 1. The housing seal portion is configured by a seal groove having a U-shaped cross section provided on a case side and a ridge which is provided on lower surface sides of the connector and the cover, is fitted into the seal groove with a predetermined gap, and has a strip shape which has a rectangular-shaped cross section. Then, the gap between the seal groove and the ridge is filled with a seal agent. At this time, the depths and the widths of the seal groove and the ridge are set to be substantially constant over the entirety of the periphery so as to secure a constant seal length. The seal groove and the ridge are also provided in the connector seal portion, as in the housing seal portion. The ridge is provided on the connector side in lower surface side of the connector, and the seal groove is formed on the connector side in a portion excluding the lower surface side thereof. At this time, the seal groove is formed on the lower surface side of the connector so that the depth thereof is deep and the groove width thereof is narrow. In addition, the seal groove is formed on the upper surface side of the connector so that the depth thereof is shallow and the groove width thereof is wide. Accordingly, a seal length of the connector seal portion is set to be constant over the entirety of the periphery thereof. Further, the provision of a fitting structure between an auxiliary seal groove and an auxiliary ridge is described so that the seal length is secured at a joint portion between the connector seal portion and the housing seal portion in paragraphs 0033 to 0038 of PTL 1. 
         [0005]    In addition, a vehicle-mounted electronic equipment using a waterproof seal in which an inorganic filler and a water absorbing or hygroscopic organic filler are blended in a resin which reacts with moisture in the atmosphere and is cured by crosslink of polymers with each other is described as a waterproof seal in the abstract of JP-A-2014-3206 (PTL 2). 
       CITATION LIST 
     Patent Literature 
       [0006]    PTL 1: JP-A-2013-69735 
         [0007]    PTL 2: JP-A-2014-3206 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0008]    In PTL 1, although improvement of the seal performance (waterproof property) is considered by making the seal length constant, consideration for reducing the seal material is not sufficient. In addition, in PTL 2, since it is a technique of replacing the seal material with a new material in order to improve the seal performance (waterproof property) while using an inexpensive material, although adhesive strength can be improved, the amount of the seal material used is not reduced. 
         [0009]    An object of the invention is to provide an electronic control device which is capable of reducing the amount of the seal material used while securing waterproof property. 
       Solution to Problem 
       [0010]    In order to achieve the object, an electronic control device of the invention includes a housing which is joined by a plurality of members and of which a peripheral portion is configured by a plurality of sides, a circuit board which is accommodated in an inside of the housing, and a seal structure which is disposed on the peripheral portion along the sides. A seal material is provided in the seal structure so as to connect between the plurality of members. A seal sectional area in an end portion of a side is smaller than that in a central portion of the side in the seal structure which is disposed on the side of the peripheral portion. 
       Advantageous Effects of Invention 
       [0011]    According to the invention, a structure for reducing the seal material without reducing waterproof property is realized, by adopting a structure in which the sectional area of the seal material is changed. Decrease in the cost, the size and weight of the control unit and further improvement of the waterproof reliability can be realized. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]      FIG. 1  is a perspective view illustrating an electronic control unit  1  according to a present Example. 
           [0013]      FIG. 2  is an exploded view illustrating the electronic control unit. 
           [0014]      FIG. 3  is a top view illustrating the electronic control unit. 
           [0015]      FIG. 4A  is a partial cross-sectional view taken along line IVA-IVA in  FIG. 3 . 
           [0016]      FIG. 4B  is a partial cross-sectional view taken along line IVB-IVB in  FIG. 3 . 
           [0017]      FIG. 4C  is a partial cross-sectional view taken along line IVC-IVC in  FIG. 3 . 
           [0018]      FIG. 5A  is a partial cross-sectional view (Example 2) taken along line IVA-IVA in  FIG. 3 . 
           [0019]      FIG. 5B  is a partial cross-sectional view (Example 2) taken along line IVB-IVB in  FIG. 3 . 
           [0020]      FIG. 5C  is a partial cross-sectional view (Example 2) taken along line IVC-IVC in  FIG. 3 . 
           [0021]      FIG. 6A  is a partial cross-sectional view (Example 3) taken along line IVA-IVA in  FIG. 3 . 
           [0022]      FIG. 6B  is a partial cross-sectional view (Example 3) taken along line IVB-IVB in  FIG. 3 . 
           [0023]      FIG. 6C  is a partial cross-sectional view (Example 3) taken along line IVC-IVC in  FIG. 3 . 
           [0024]      FIG. 7A  is a partial cross-sectional view (Example 4) taken along line IVA-IVA in  FIG. 3 . 
           [0025]      FIG. 7B  is a partial cross-sectional view (Example 4) taken along line IVB-IVB in  FIG. 3 . 
           [0026]      FIG. 7C  is a partial cross-sectional view (Example 4) taken along line IVC-IVC in  FIG. 3 . 
           [0027]      FIG. 8A  is a partial cross-sectional view (Example 5) taken along line IVA-IVA in  FIG. 3 . 
           [0028]      FIG. 8B  is a partial cross-sectional view (Example 5) taken along line IVB-IVB in  FIG. 3 . 
           [0029]      FIG. 8C  is a partial cross-sectional view (Example 5) taken along line IVC-IVC in  FIG. 3 . 
           [0030]      FIG. 9A  is a partial cross-sectional view (Example 6) taken along line IXA-IXA in  FIG. 3 . 
           [0031]      FIG. 9B  is a partial cross-sectional view (Example 6) taken along line IXB-IXB in  FIG. 3 . 
           [0032]      FIG. 9C  is a partial cross-sectional view (Example 6) taken along line IXC-IXC in  FIG. 3 . 
           [0033]      FIG. 10A  is a partial cross-sectional view (Example 7) taken along line IXA-IXA in  FIG. 3 . 
           [0034]      FIG. 10B  is a partial cross-sectional view (Example 7) taken along line IXB-IXB in  FIG. 3 . 
           [0035]      FIG. 10C  is a partial cross-sectional view (Example 7) taken along line IXC-IXC in  FIG. 3 . 
           [0036]      FIG. 11  is an enlarged view illustrating a seal material branching portion of Example 8. 
           [0037]      FIG. 12  is a top view illustrating the seal material branching portion of Example 8. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0038]    Hereinafter, examples according to the invention will be described using the drawings. Here, an electronic control unit for an automobile (electronic control unit for vehicle mounting) will be described as an example. 
         [0039]    A housing of the electronic control unit is configured by a base (corresponding to case of PTL 1) and a cover, and has a configuration in which a connector is exposed from the housing. A seal material is provided on the joining portion in which the base, the cover, and the connector are joined, respectively. Deformation that each joining portion of the cover, the base and the connector is opened toward the outside is generated due to rise in the ambient temperature of the electronic control unit and rise in the internal pressure thereof. Due to the deformation, high stress is generated in the seal material. In the related art, for example, the width, the thickness, and the sectional area of the seal material are designed so that the maximum stress generated in the seal material is a value enough not to exceed the adhesive force of the seal material. In order to reduce the cost, the size and the weight of the electronic control unit, it is necessary to reduce the seal material. As a method of reducing the seal material, it is considered to uniformly reduce the application amount of the seal material, for example. However, when the application amount of the seal material is uniformly reduced, there is a possibility that the generated stress exceeds the adhesive force of the seal material at the portion where the generated stress becomes a maximum. When the generated stress exceeds the adhesive force of the seal material, since the seal material is peeled off from an application surface of the cover, the base or the connector, waterproof property is unlikely to be kept. Therefore, it is necessary to reduce the seal material while maintaining waterproof property. 
         [0040]    In addition, a mounting environment of the electronic control unit for an automobile tends to become more severe. According to this, in the related art, in order to maintain the waterproof property, it is necessary to greatly increase the amount of the seal material used. Therefore, a technique to minimize the increase of the seal material is required. 
         [0041]    The electronic control unit  1  according to the examples can cope with a severe environment and can be used to be mounted on various devices used in the severe environment like the environment of automobiles. 
       Example 1 
       [0042]    An example of the electronic control unit according to the invention will be described using  FIG. 1  to  FIG. 4 .  FIG. 1  is a perspective view illustrating an electronic control unit  1  according to the example.  FIG. 2  is an exploded view illustrating the electronic control unit  1 .  FIG. 3  is a top view illustrating the electronic control unit  1 .  FIG. 4A ,  FIG. 4B , and  FIG. 4C  are partial cross-sectional views taken along line IVA-IVA, line IVB-IVB, and line IVC-IVC in  FIG. 3 .  FIG. 1  to  FIG. 3  are commonly used in Example 2 to Example 8. 
         [0043]    The electronic control unit  1  includes a plurality of components (members) forming a space in an inside of the housing  60 , and is configured by a base  10 , a cover  20 , and a connector  30 , for example. In the following description, a vertical direction is defined based on  FIG. 1 . In other words, in the housing  60 , a base  10  side is defined as a lower side, and a cover  20  side is defined as an upper side. In addition, for convenience, a surface in which there is the cover  20  and a surface of an upper side of the electronic control unit  1  are defined as an upper surface, and a surface of a lower side of the base  10  is defined as a lower surface of the electronic control unit  1 . The vertical direction is not related to a mounting direction at the time of mounting the electronic control unit  1 . 
         [0044]    A seal material  50  for waterproofing is interposed between the base  10 , the cover  20  and the connector  30 , respectively and the base  10 , the cover  20  and the connector  30  are joined to each other. In a case of being viewed from the upper surface side or the lower surface side, as illustrated in  FIG. 3 , the housing  60  has a substantially quadrangular shape, and has a side  60   a,  a side  60   b,  a side  60   c,  and a side  60   d . An outer shape of the base  10  has a substantially quadrangular shape and has four sides along the side  60   a  to the side  60   d . An outer shape of the cover  20  has a substantially quadrangular shape and has four sides along the side  60   a  to the side  60   d . However, as illustrated in  FIG. 2 , the cover  20  has an opening  20   a  formed on a side along the side  60   a  of the housing  60 . The opening  20   a  is formed by a recess recessed from the lower side toward the upper side. 
         [0045]    The joining structure between the base  10  and the cover  20  will be described. A seal structure  100  and seal structures  200 T and  200 U are formed on the peripheral portion of the housing  60 . 
         [0046]    A seal groove structure  2  constituting the seal structure  100  is formed on a peripheral portion of the base  10 . The seal groove structure  2  is formed at least on a side along the side  60   b  to the side  60   d.  The side along the side  60   a  is a portion to be joined with the connector  30 , and the seal structures  200 T and  200 U are configured therein. The seal structures  200 T and  200 U will be described below. There is also a case where the seal groove structure  2  is simply referred to as a seal groove  2 . On the other hand, a ridge  3  to be fitted into the seal groove structure  2  with a gap  70  is provided on the peripheral portion of the cover  20 . The ridge  3  is formed at least on a side along the side  60   b  to the side  60   d.    
         [0047]    As illustrated in  FIG. 4A ,  FIG. 4B , and  FIG. 4C , the ridge  3  is fitted with a gap  70  between a groove side surface and a groove bottom surface of the seal groove structure  2 . The gap  70  is filled with the seal material  50 , and the base  10  and the cover  20  are joined together. The seal material  50  is a liquid silicone resin, for example, and after the seal material is applied to the seal groove structure  2 , the ridge  3  of the cover  20  is fitted therein and the seal material  50  is cured to realize waterproof property. 
         [0048]    The side along the side  60   a  is a portion to be joined with the connector  30 , and it will be described below. 
         [0049]    Reference numeral  40  denotes a circuit board constituting the electronic control unit  1 , which is housed in a space formed by the base  10 , the cover  20 , the connector  30 , and the seal material  50 . The circuit board  40  is made of an insulating board  41  formed as a substantially quadrangular shape plate body by an insulating resin material or the like, for example, and a wiring pattern is provided on an upper surface and a lower surface thereof. A plurality of electronic components  41  made of a capacitor, a coil, a transistor, a semiconductor IC or the like, for example is mounted on the circuit board  40 . 
         [0050]    The connector  30  is configured by a connector housing  31  and a connector pin  32 . The connector  30  is connected to various sensors, actuators, or the like provided on the vehicle side and thus the electronic control unit  1  controls the engine. 
         [0051]    Reference numeral  13  is two bracket portions provided on the outer surface side of the base  10 , for example, and constitutes an attaching portion which attaches the electronic control unit  1  to a vehicle body of an automobile or the like. 
         [0052]    The cover  20  is fixed to the base  10  and formed by injection molding of resin, for example. The cover  20  is fixed to the base  10  by a cover fixing hole  12  provided in the base  10  and a thermal caulking portion  23  for example. In other words, the fixing hole  12  and the thermal caulking portion  23  constitute a fixing portion which fixes the cover  20  and the base  10 . The fixing method of the cover  20  is not limited to thermal caulking. For example, fixing methods such as caulking, snap fitting, screws, tapping screws, rivets, adhesive bonding, press-fitting, or the like may be used. 
         [0053]    The seal structure of the base  10  and the cover  20  will be described in detail. 
         [0054]    In this example, as illustrated in  FIG. 4A ,  FIG. 4B , and  FIG. 4C , the seal structure  100  of the base  10  and the cover  20  is configured by the seal groove structure  2 , the ridges  3  and the seal material  50 . In this seal structure  100 , at least one of the width of the groove and the depth of the groove is changed according to the distance from the fixing portion. The seal material  50  of the entirety of the electronic control unit  1  is reduced by making the width of the groove narrow and making the depth of the groove shallow in the vicinity of the fixing portions  12  and  23 . In this case, it is also possible to decrease the height of the ridge  3  in the vicinity of the fixing portions according to the depth of the seal groove structure  2 . 
         [0055]    In other words, in this example, in a case where the cross sectional area of the gap which is formed on the inside of the groove of the seal groove structure  2  and is filled with the seal material  50  is compared at two points of which distances from the fixing portions  12  and  23  are different from each other, a side of the cross sectional area at a position which is close to the fixing portions  12  and  23  is made smaller than the cross sectional area at a position which is away from the fixing portions  12  and  23 . Hereinafter, this sectional area is referred to as a seal sectional area. A groove width, a groove depth, a ridge height and a ridge width (thickness) can be changed so as to satisfy this relationship. The sectional area is an area of a section (cross section) in a direction perpendicular to an extending direction (longitudinal direction) of the groove. 
         [0056]      FIG. 4A  illustrates a seal structure  100 A at a position which is farthest from the fixing portions  12  and  23  in the side  60   c  of the housing  60 .  FIG. 4B  illustrates a seal structure  100 B at a position which is away from the fixing portions  12  and  23  next to  FIG. 4A .  FIG. 4C  illustrates a seal structure  100 C at a position which is closest to the fixing portions  12  and  23 . 
         [0057]    In the seal structure  100 C at a position which is closest to the fixing portions  12  and  23 , a groove width Wc is the narrowest among the three seal structures  100 A,  100 B, and  100 C. In the seal structure  100 A at a position which is farthest from the fixing portions  12  and  23 , a groove width Wa is the widest among the three seal structures  100 A,  100 B and  100 C. In the seal structure  100 B in which the distance from the fixing portions  12  and  23  is intermediate between the seal structure  100 A and the seal structure  100 C, a groove width Wb is an intermediate width between the groove width Wa of the seal structure  100 A and the groove width Wc of the seal structure  100 C. 
         [0058]    In the seal structure  100 C at a position which is closest to the fixing portions  12  and  23 , a groove depth Dc is the shallowest among the three seal structures  100 A,  100 B, and  100 C. In the seal structure  100 A at a position which is farthest from the fixing portions  12  and  23 , a groove depth Da is the deepest among the three seal structures  100 A,  100 B, and  100 C. In the seal structure  100 B in which the distance from the fixing portions  12  and  23  is intermediate between the seal structure  100 A and the seal structure  100 C, a groove depth Db is an intermediate depth between the groove depth Da of the seal structure  100 A and the groove depth Dc of the seal structure  100 C. 
         [0059]    In other words, the groove width and the groove depth are in a relationship of Wa&gt;Wb&gt;We and Da&gt;Db&gt;Dc. The height of the ridge  3  has a relationship that a ridge height Ha of the seal structure  100 A, a ridge height Hb of the seal structure  100 B and a ridge height Hc of the seal structure  100 C are Ha&gt;Hb&gt;Hc. The ridge heights Ha, Hb, and Hc maybe the same height as long as the relationship of the seal sectional area described above is satisfied. However, a gap has to be formed between a tip of the ridge  3  and a bottom of the groove  2 . 
         [0060]    An adhesive length (seal length) between an inner wall of the seal groove structure  2  and the seal material  50  is reduced in both a case where the depth of the seal groove structure  2  is shallow and a case where the width of the seal groove structure  2  is narrowed. The length of the seal length contributes to the corrosion resistance of the electronic control unit  1 . In a case where the seal groove structure  2  is narrowed, the seal material  50  can be reduced without the corrosion resistance being significantly decreased since the reduction in the seal length is decreased with respect to the reduction amount of the seal material  50 , as compared with a case where the seal groove structure  2  is made shallow. 
         [0061]    In addition, in a case where this example is applied to a case where the mounting environment of the electronic control unit  1  becomes severer than the mounting environment in the related art, the groove width of the seal groove structure  2  in the vicinity of the fixing portions is made the same as that in the related art and the width of the seal groove structure  2  at a portion which is far from the fixing portions is increased, for example. There is a high concern that the seal material  50  is peeled off in a portion which is far from the fixing portions of the base  10  and the cover  20 . Therefore, the increase amount of the seal material  50  can be suppressed to a minimum by increasing the seal material  50  only around the portion where there is a high concern that the seal material  50  is peeled off. 
         [0062]    In the above description, the seal sectional area is changed based on the distance from the fixing portions. In the vicinity of the fixing portions  12  and  23 , the fixing portions  12  and  23  suppress the deformation of each of the joining portions of the cover, the base and the connector, and suppress the stress generated in the seal material  50 . In this sense, in this example, the seal sectional area is determined based on the stress generated in the seal material  50 . In other words, in the seal structure formed along the sides  60   b,    60   c , or  60   d  of the housing  60 , the seal sectional area at the position where stress generated in the seal material  50  is large is made larger than the seal sectional area at the position where stress generated in the seal material  50  is small. 
         [0063]    Normally, the fixing portions  12  and  23  are provided at the four corners of the housing  60 . In the four corners, the seal groove structure  2  and the ridge  3  constitute a bent portion, which is also a portion where rigidity is high with respect to the force to open outward. Therefore, in the seal structure configured along the sides  60   b,    60   c,  and  60   d  of the housing  60 , deformation is unlikely to be generated as it approaches both end portions of the side. Therefore, the stress generated in the seal material  50  also tends to become smaller as it approaches both end portions of the side. Therefore, in the seal structure configured along one side, it is preferable that the seal sectional area of the portion positioned on the center side is larger than the seal sectional area of the portion positioned on the end portion side. This means that the seal sectional area is made large at the position where the stress generated in the seal material  50  is large among the sides  60   b,    60   c,  and  60   d  of the housing  60 . 
       Example 2 
       [0064]    A second example according to the invention will be described using  FIG. 5A ,  FIG. 5B , and  FIG. 5C .  FIG. 5A ,  FIG. 5B , and  FIG. 5C  are partial cross-sectional views illustrating cross sections taken along line IVA-IVA, line IVB-IVB, and line IVC-IVC in  FIG. 3 , as in  FIG. 4A ,  FIG. 4B  and  FIG. 4C . 
         [0065]    In this example, in order to make the seal sectional area at a position which is close to the fixing portions  12  and  23  smaller than the seal sectional area at a position which is away from the fixing portions  12  and  23 , the width of the ridge  3  in the vicinity of the fixing portion  12  and  23  of the cover  20  is increased, or the height of the ridge  3  therein is increased. Accordingly, the amount of the seal material  50  in the vicinity of the fixing portions can be reduced. 
         [0066]    Specifically, in the seal structure  100 C at a position which is closest to the fixing portions  12  and  23 , the ridge width Wf is the largest among the three seal structures  100 A,  100 B, and  100 C. In the seal structure  100 A at a position which is farthest from the fixing portions  12  and  23 , the ridge width Wd is the smallest among the three seal structures  100 A,  100 B, and  100 C. In the seal structure  100 B in which the distance from the fixing portions  12  and  23  is intermediate between the seal structure  100 A and the seal structure  100 C, the ridge width We is an intermediate size between the ridge width Wd of the seal structure  100 A and the ridge width Wf of the seal structure  100 C. 
         [0067]    In addition, in the seal structure  100 C at a position which is closest to the fixing portions  12  and  23 , the ridge height Hc is the highest among the three seal structures  100 A,  100 B, and  100 C. In the seal structure  100 A at a position which is farthest from the fixing portions  12  and  23 , the ridge height Ha is the lowest among the three seal structures  100 A,  100 B, and  100 C. In the seal structure  100 B in which the distance from the fixing portions  12  and  23  is intermediate between the seal structure  100 A and the seal structure  100 C, the ridge height Hb is an intermediate height between the ridge height Ha of the seal structure  100 A and the ridge height Hc of the seal structure  100 C. 
         [0068]    In other words, the ridge width has a relationship of Wd&lt;We&lt;Wf. In addition, the ridge height has a relationship of Ha&lt;Hb&lt;Hc. The groove depths Da, Db and Dc are the same depth. The groove depths Da, Db, and Dc may be changed within a range where the seal sectional area satisfies the relationships described above. In addition, a gap has to be formed between the tip of the ridge  3  and the bottom of the groove  2 . 
         [0069]    The material of the cover  20  is a resin such as PBT, for example and PBT is generally a cheap material with respect to the material used for the seal material  50 . In this example, although the material of the cover  20  increases according to the reduction amount of the seal material  50 , the cost of the electronic control unit  1  as a whole can be reduced. 
         [0070]    Furthermore, in the case of this example, the height and width of the ridge  3  can be changed by a slope being provided. For example, in the case of using the liquid seal material  50 , the seal material  50  can be extended before being cured by the slope at the time of the electronic control unit  1  being assembled. In other words, in equipment which applies the seal material  50  to an application track matching the seal groove structure  2 , the application speed can be made constant by this slope and a manufacturing facility becomes simple. 
       Example 3 
       [0071]    A third example of the present invention will be described with reference to  FIG. 6A ,  FIG. 6B , and  FIG. 6C .  FIG. 6A ,  FIG. 6B , and  FIG. 6C  are partial cross-sectional views illustrating cross sections taken along line IVA-IVA, line IVB-IVB and line IVC-IVC in  FIG. 3 , as in  FIG. 4A ,  FIG. 4B , and  FIG. 4C . 
         [0072]    In the joining structure between the base  10  and the cover  20 , for example, a base joining surface  11  is provided at the joining portion of the base  10 , and the cover  20  has a cover joining surface  21  facing the base joining surface  11  with a gap therebetween, and there is also a surface seal structure in which the base  10  and the cover  20  are joined by the seal material  50  being interposed therebetween. In other words, in this example, opposing surfaces facing each other (base joining surface  11  and cover joining surface  21 ) are configured in the joining portion between the base  10  and the cover  20 , and the gap between the base joining surface  11  and the cover joining surface  21  is filled with the seal material  50 . In this example, the groove  2  and the ridge  3  are not formed on the joining portion between the base  10  and the cover  20 . The invention is also applicable in such a case. 
         [0073]    In this example, in order to make the sectional area of the seal material  50  at a position which is close to the fixing portions  12  and  23  smaller than the sectional area of the seal material  50  at a position which is away from the fixing portions  12  and  23 , the gap between the base joining surface  11  and the cover joining surface  21  is narrowed in the vicinity of the fixing portions  12  and  23  of the base  10  and the cover  20 . Accordingly, the thickness of the seal material  50  is decreased and the amount of the seal material  50  in the vicinity of the fixing portions can be reduced. 
         [0074]    Specifically, in the seal structure  100 C at a position which is closest to the fixing portions  12  and  23 , the gap Gc is the smallest among the three seal structures  100 A,  100 B, and  100 C. In the seal structure  100 A at a position which is farthest from the fixing portions  12  and  23 , the gap Ga is the largest among the three seal structures  100 A,  100 B, and  100 C. In the seal structure  100 B in which the distance from the fixing portions  12  and  23  is intermediate between the seal structure  100 A and the seal structure  100 C, the gap Gb is an intermediate size between the gap Ga of the seal structure  100 A and the gap Gc of the seal structure  100 C. In this case, the sizes of the gaps Ga, Gb, and Gc are equal to the thickness of the seal material  50  which is filled in the gaps Ga, Gb, and Gc. In other words, the gap (thickness of seal material  50 ) has a relationship of Gc&lt;Gb&lt;Ga. 
         [0075]    In addition, in the seal structure  100 C at a position which is closest to the fixing portions  12  and  23 , the height Hf of the base joining surface  11  is the highest among the three seal structures  100 A,  100 B, and  100 C. In the seal structure  100 A at a position which is farthest from the fixing portions  12  and  23 , the height Hd of the base joining surface  11  is the lowest among the three seal structures  100 A,  100 B, and  100 C. In the seal structure  100 B in which the distance from the fixing portions  12  and  23  is intermediate between the seal structure  100 A and the seal structure  100 C, the height He of the base joining surface  11  is an intermediate height between the height Hd in the seal structure  100 A and the height Hf in the seal structure  100 C. 
         [0076]    In this example, the widths Wg, Wh, and Wi of the seal material  50  in the seal structures  100 A,  100 B, and  100 C are set to the same size. However, since the flow of the seal material  50  is not regulated, a slight change is generated between the widths Wg, Wh, and Wi. 
       Example 4 
       [0077]    A fourth example according to the invention will be described using  FIG. 7A ,  FIG. 7B , and  FIG. 7C .  FIG. 7A ,  FIG. 7B , and  FIG. 7C  are partial cross-sectional views illustrating cross sections taken along line IVA-IVA, line IVB-IVB, and line IVC-IVC in  FIG. 3 , as in  FIG. 4A ,  FIG. 4B  and,  FIG. 4C . 
         [0078]    In this example, as in the Example 3, opposing surfaces facing each other (base joining surface  11  and cover joining surface  21 ) are configured in the joining portion between the base  10  and the cover  20 , and the gap between the base joining surface  11  and the cover joining surface  21  is filled with the seal material  50 . In this example, the groove  2  and the ridge  3  are not formed on the joining portion between the base  10  and the cover  20 . In this example, the seal sectional area is the sectional area (cross-sectional area) of the seal material  50  formed on the gap between the seal joining surface  11  and the cover joining surface  21 . 
         [0079]    In the surface seal structure of this example, in order to make the sectional area of the seal material  50  at a position which is close to the fixing portions  12  and  23  smaller than the sectional area of the seal material  50  at a position which is away from the fixing portions  12  and  23 , the width of the seal material  50  in the vicinity of the fixing portions  12  and between the base  10  and the cover  20  is narrowed. Accordingly, the amount of the seal material  50  in the vicinity of the fixing portions  12  and  23  can be reduced. The sizes of the gaps Ga, Gb, and Gc are the same. 
         [0080]    Specifically, in the seal structure  100 C at a position which is closest to the fixing portions  12  and  23 , a seal material width Wi is the narrowest among the three seal structures  100 A,  100 B, and  100 C. In the seal structure  100 A at a position which is farthest from the fixing portions  12  and  23 , a seal material width Wg is the largest among the three seal structures  100 A,  100 B, and  100 C. In the seal structure  100 B in which the distance from the fixing portions  12  and  23  is intermediate between the seal structure  100 A and the seal structure  100 C, a seal material width Wh is an intermediate size between the seal material width Wg of the seal structure  100 A and the seal material width Wi of the seal structure  100 C. In this example, since the sizes of the gaps Ga, Gb, and Gc are the same, the thicknesses of the seal material  50  filled in the gaps Ga, Gb, and Gc are also the same. In other words, the seal material width has a relationship of Wi&lt;Wh&lt;Wg. 
         [0081]    For example, a liquid seal material  50  may be used as the seal material  50 . In this case, after the seal material  50  is applied to one of the base  10  or the cover  20 , the seal material  50  is extended by the other thereof being assemble and thus the width of the seal material  50  is determined. In a case where this example is realized by the equipment described above, the width of the seal material  50  can be changed by only the speed of applying the seal material  50  being changed. 
         [0082]    Both this example and Example 3 may be combined to change both the gaps Ga, Gb, and Gc and the seal material widths Wg, Wh, and Wi. 
       Example 5 
       [0083]    A fifth example according to the invention will be described using  FIG. 8A ,  FIG. 8B , and  FIG. 8C .  FIG. 8A ,  FIG. 8B , and  FIG. 8C  are partial cross-sectional views illustrating cross sections taken along line IVA-IVA, line IVB-IVB, and line IVC-IVC in  FIG. 3 , as in  FIG. 4A ,  FIG. 4B  and  FIG. 4C . 
         [0084]    In this example, as in Example 3, opposing surfaces facing each other (base joining surface  11  and cover joining surface  21 ) are configured in the joining portion between the base  10  and the cover  20 , and the gap between the base joining surface  11  and the cover joining surface  21  is filled with the seal material  50 . In this example, the groove  2  and the ridge  3  are not formed on the joining portion between the base  10  and the cover  20 . In this example, the seal sectional area is the sectional area (cross-sectional area) of the seal material  50  formed on the gap between the seal joining surface  11  and the cover joining surface  21 . 
         [0085]    Furthermore, in the surface seal structure of this example, for example, cover joining surface recesses  22   a,    22   b , and  22   c  forming a groove are provided along the seal portion of the cover joining surface  23 . In order to make the sectional area of the seal material  50  at a position which is close to the fixing portions  12  and  23  smaller than the sectional area of the seal material  50  at a position which is away from the fixing portions  12  and  23 , the sectional area of the cover joining surface recesses  22  in the vicinity of fixing portions  12  and  23  is decreased. Accordingly, the amount of the seal material  50  in the vicinity of the fixing portions  12  and  23  can be reduced. 
         [0086]    Specifically, in the seal structure  100 C at a position which is closest to the fixing portions  12  and  23 , the sectional area of the recess  22   c  is the smallest among the three seal structures  100 A,  100 B, and  100 C. In the seal structure  100 A at a position which is farthest from the fixing portions  12  and  23 , the sectional area of the recess  22   a  is the largest among the three seal structures  100 A,  100 B, and  100 C. In the seal structure  100 B in which the distance from the fixing portions  12  and  23  is intermediate between the seal structure  100 A and the seal structure  100 C, the sectional area of the recess  22   b  is an intermediate size between the sectional area of the recess  22   a  of the seal structure  100 A and the sectional area of the recess  22   c  of the seal structure  100 C. In other words, there is a relationship of the sectional area of the recess  22   c &lt; the sectional area of the recess  22   b &lt; the cross sectional area of the recess  22   a.  In this example, the sizes of the gaps Ga, Gb, and Gc and the seal material widths Wg, Wh, and Wi are the same. 
         [0087]    The recess  22   a,  the recess  22   b  and the recess  22   c  may be provided on abase joining surface  11  side. Alternatively, the recess  22   a,  the recess  22   b,  and the recess  22   c  may be provided on both of the base joining surface  11  and the cover joining surface  21 . In addition, in this example, the recess  22   c  may not be provided and the sectional area of the recess  22   c  may be made zero. 
         [0088]    As in the first example, this example can also be applied to a case where the mounting environment of the electronic control unit  1  becomes severer than the mounting environment in the related art. In the vicinity of the fixing portions  12  and  23 , the sectional area of the cover joining surface recess  22   c  is decreased or the cover joining surface recess  22   c  is eliminated, and the cross sectional areas of the cover joining surface recesses  22   a  and  22   b  are increased at a portion which is far from the fixing portion. Accordingly, the amount of the seal material  50  is increased only in the surroundings of the portion in which there is a high concern that the seal material  50  is peeled off and which is far from the fixing portions  12  and  23 . Accordingly, the increase in the amount of the seal material  50  can be suppressed to a minimum. 
         [0089]    The gap Ga, Gb, and Gc and the seal material widths Wg, Wh, and Wi may be changed by any of Example 3 and Example 4 or combination of both Example 3 and Example 4 in this example. 
       Example 6 
       [0090]    A sixth example according to the invention will be described using  FIG. 9A ,  FIG. 9B , and  FIG. 9C .  FIG. 9A , FIG.  9 B and  FIG. 9C  are partial cross-sectional views illustrating cross sections taken along line IXA-IXA, line IXB-IXB and line IXC-IXC in  FIG. 3 . Only the vicinity of the seal structure is illustrated in  FIG. 9B  and  FIG. 9C . The seal structures  200 T and  200 U in the peripheral portion of the connector  30  described in this example are combined with the seal structures  100  ( 100 A,  100 B, and  100 C) of the Example 1 to Example 5 described above to complete the seal structure at the peripheral portion of the housing  60 . 
         [0091]    The invention can be applied not only to the joining between the base  10  and the cover  20  but also to the joining portion between the connector  30  and the base  10  or the joining portion between the connector  30  and the cover  20 . In the seal structure of this example, as illustrated in  FIG. 9A ,  FIG. 9B , and  FIG. 9C , the connector housing  31  includes the ridge  3 , and the cover  20  includes the seal groove structure  2 . In order to make the seal sectional area at a position which is close to the fixing portions  12  and  23  smaller than the seal sectional area at a position which is away from the fixing portions  12  and  23 , the groove widths Wk and Wl of portions which are other than in the vicinity of the center portion of the connector housing  31  are further narrowed than the groove width Wj in the vicinity of the center portion thereof. Accordingly, the seal material  50  can be reduced. 
         [0092]    Hereinafter, this will be described in detail. 
         [0093]    The connector  30  protrudes from the housing  60  at the side  60   a  side of the housing  60 . Therefore, among the outer peripheral surface of the connector  60 , the upper surface portion and the side surface portion thereof face the lower surface side (edge surface of opening  20   a ) of the cover  20  to form a seal structure  200 T ( 200 TA,  200 TB and  200 TC). In addition, among the outer peripheral surface of the connector  60 , the lower surface portion thereof faces the upper surface side of the base  10  to form a seal structure  200 U. 
         [0094]    The seal structure  200 T is configured by a seal groove structure (seal groove)  2  formed on the lower surface side of the cover  20  and a ridge  3  formed on the outer peripheral surface of the connector. In addition, the seal structure  200 U is configured by an upper surface of a flat portion  10 E formed on the edge of the base  10  and the lower surface  30 U of the connector facing each other. A gap formed by the seal groove structure  2  and the ridge  3  and a gap formed by the upper surface of the flat portion  10 E of the base  10  and the lower surface  30 U of the connector are filled with a seal material  50 . 
         [0095]    Regarding the gap formed by the seal groove structure  2  and the ridge  3 , the sectional area of the gap formed on an inside of the groove of the seal groove structure  2  and filled with the seal material  50  is referred to as a seal sectional area as in the examples described above. 
         [0096]    In the seal structure  200 TC at a position which is closest to the fixing portions  12  and  23 , the groove width Wl of the seal groove structure  2  is the narrowest among the three seal structures  200 TA,  200 TB, and  200 TC. In the seal structure  200 TA at a position which is farthest from the fixing portions  12  and  23 , the groove width Wj is the largest among the three seal structures  200 TA,  200 TB, and  200 TC. In the seal structure  200 TB in which the distance from the fixing portions  12  and  23  is intermediate between the seal structure  200 TA and the seal structure  200 TC, the groove width Wk is an intermediate size between the groove width Wj of the seal structure  200 TA and the groove width Wl of the seal structure  200 TC. In other words, the groove widths of the seal structures  200 TA,  200 TB, and  200 TC have a relationship of Wl&lt;Wk&lt;Wj. 
         [0097]    In this example, the groove depths Dd, De, and Df of the seal structures  200 TA,  200 TB, and  200 TC are the same. In addition, the ridge heights Hg, Hh, and Hi of the seal structures  200 TA,  200 TB, and  200 TC are the same. The groove depths Dd, De, and Df and the ridge heights Hg, Hh, and Hi may be different from each other within a range where the seal sectional area at a position which is close to the fixing portions  12  and  23  is smaller than the seal sectional area at a position which is away from the fixing portions  12  and  23 . 
         [0098]    In this example (also as in Example 7 to be described below), although the seal structure  200 U is configured such that the upper surface of the flat portion  10 E formed on the edge of the base  10  faces the lower surface  30 U of the connector, the seal groove structure  2  and the ridge  3  can be configured to combine with each other as in the seal structure  100 . Incidentally,  FIG. 2  illustrates a configuration using the seal groove structure  2  and the ridge  3 . 
       Example 7 
       [0099]    A seventh example according to the invention will be described using  FIG. 10A ,  FIG. 10B , and  FIG. 10C .  FIG. 10A ,  FIG. 10B , and  FIG. 10C  are partial cross-sectional views illustrating cross sections taken along line IXA-IXA, line IXB-IXB and line IXC-IXC in  FIG. 3 , as in  FIG. 9A ,  FIG. 9B , and  FIG. 9C . The seal structure  200 T and  200 U of this example are combined with the seal structure  100  ( 100 A,  100 B, and  100 C) of the Example 1 to Example 5 described above to complete the seal structure at the peripheral portion of the housing  60 . 
         [0100]    In this example, the connector housing  31  includes the seal groove structure  2 , and the cover  20  includes the ridge  3 . In order to make the seal sectional area at a position which is close to the fixing portions  12  and  23  smaller than the seal sectional area at a position which is away from the fixing portions  12  and  23 , the groove widths Wq and Wr of portions which are other than in the vicinity of the central portion of the connector housing  31  are further narrowed than the groove width Wp in the vicinity of the central portion thereof. Accordingly, the seal material  50  can be reduced. In this example, by the portion where the surface seal structure is common in the related art being set as a groove seal structure, it is possible to reduce the size of the connector housing  31  and shorten the connector pin  32  along with the reduction of the seal material  50 . 
         [0101]    Hereinafter, this will be described in detail. 
         [0102]    In the seal structure  200 TC at a position which is closest to the fixing portions  12  and  23 , the groove width Wr of the seal groove structure  2  is the narrowest among the three seal structures  200 TA,  200 TB, and  200 TC. In the seal structure  200 TA at a position which is farthest from the fixing portions  12  and  23 , the groove width Wp is the largest among the three seal structures  200 TA,  200 TB, and  200 TC. In the seal structure  200 TB in which the distance from the fixing portions  12  and  23  is intermediate between the seal structure  200 TA and the seal structure  200 TC, the groove width Wq is an intermediate size between the groove width Wp of the seal structure  200 TA and the groove width Wr of the seal structure  200 TC. In other words, the groove widths of the seal structures  200 TA,  200 TB, and  200 TC have a relationship of Wr&lt;Wq&lt;Wp. 
         [0103]    In this example, the groove depths Dg, Dh, and Di of the seal structures  200 TA,  200 TB, and  200 TC are the same. In addition, the ridge heights Hj, Hk, and Hl of the seal structures  200 TA,  200 TB, and  200 TC are the same. In addition, the ridge widths Ws, Wt, and Wu of the seal structures  200 TA,  200 TB, and  200 TC are the same. The groove depths Dg, Dh, and Di, the ridge heights Hj, Hk, and Hl, and the ridge widths Ws, Wt, and Wu may be made different from each other within a range where the seal sectional area at a position which is close to the fixing portions  12  and  23  is smaller than the seal sectional area at a position which is away from the fixing portions  12  and  23 . 
       Example 8 
       [0104]    An eighth example according to the invention will be described using  FIG. 11  and  FIG. 12 .  FIG. 11  is an enlarged view of a seal material branching portion  51 .  FIG. 12  is a view of the periphery illustrated in  FIG. 11  as viewed from the upper surface side. 
         [0105]    In the case where there are three or more members forming the space of the inside portion of the housing such as the base  10 , the cover  20 , and the connector  30 , for example, there is a case where the seal material  50  has the seal material branching portion  51  as illustrated in  FIG. 11 . Since peeling of the seal material  50  is likely to be generated in such a portion  51 , the waterproof reliability can be maintained by keeping the width Wv of the seal groove structure  2  in this portion wide. 
         [0106]    In each of the examples described above, in a case where the ridge height, the ridge width, the groove width, the groove depth, the seal material width, or the seal material thickness is changed, it is preferable to connect between large size portions and small size portions by a slope surface. In a case where the liquid seal material  50  is used, the seal material  50  can be extended by this slope surface. 
         [0107]    The invention includes various modification examples without being limited to the examples described above. For example, the examples described above have been described in detail in order to explain the invention in an easy-to-understand manner, and are not necessarily limited to those including all the configurations. In addition, it is possible to replace a portion of the configuration of one example with the configuration of another example, and in addition, the configuration of another example can be added to the configuration of one example. In addition, it is possible to add, delete, and replace other configurations with respect to a portion of the configuration of each example. 
       REFERENCE SIGNS LIST 
       [0108]      1  . . . electronic control unit,  2  seal groove structure,  3  . . . ridge,  10  . . . base,  10 E . . . flat portion formed on periphery of base,  11  . . . base joining surface,  12  . . . cover fixing hole,  13  . . . bracket portion,  20  . . . cover,  21  . . . cover joining surface,  22  . . . cover joining surface recess,  23  . . . heat caulking portion,  30  . . . connector,  31  . . connector housing,  32  . . . connector pin,  40  . . . circuit board,  41  . . . insulating board,  42  . . . electronic component,  50  . . . seal material,  51  . . . seal material branching portion,  70  . . . gap,  100 ,  100 A,  100 B, and  100 C . . . seal structure,  200 ,  200 T,  200 TA,  200 TB,  200 TC,  200 U . . . seal structure.