Patent Publication Number: US-2023156948-A1

Title: Electronic Control Unit

Description:
TECHNICAL FIELD 
     The present invention relates to a structure of an electronic control unit having a waterproof structure. 
     BACKGROUND ART 
     As a background art of the present technical field, a waterproof control unit described in JP 2017-76758 A (PTL 1) is known. 
     The waterproof control unit of PTL 1 includes a housing that hermetically houses a circuit board by a base, a cover, and a connector housing. The cover includes: a third seal recessed surface part forming a third seal gap with the base; a first seal recessed surface part provided in a trapezoidal oblique side part on the cover side in a first seal gap between the cover and three sides of a trapezoid of the connector housing having a trapezoidal end surface; and a replenishment inclined surface part which is a part of the trapezoidal oblique side part. As a result, in the waterproof control unit of PTL 1, when the connector housing is installed after a waterproof sealing material is applied to a first seal gap surface, the waterproof sealing material is prevented from being scraped off and becoming thin by being replenished with the waterproof sealing material applied to the replenishment inclined surface part (see Abstract). 
     CITATION LIST 
     Patent Literature 
     PTL 1: JP 2017-76758 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     In an electronic control unit having a right angle connector in which the connection direction is parallel to a board surface as in the waterproof control unit (hereinafter, referred to as an electronic control unit) of PTL 1, three seal parts, that is, a “connector lower seal part” and a “connector upper seal part” for waterproofing the periphery of the connector, and an “outer peripheral seal part” for waterproofing a part between the cover other than the connector part and the base, are required. Therefore, a three-way junction of the sealant is formed in a part where the three seal parts intersect in the vicinity of the connector. 
     In the three-way junction of the sealant, due to the application locus of the sealant, twice or more application of the sealant cannot be avoided, and the application amount of the sealant becomes excessive. Therefore, in the three-way junction of the sealant, there is a problem that an overflow amount of the sealant after the base, the connector housing, and the cover are assembled increases. 
     In the electronic control unit described in PTL 1, although consideration is given to preventing the sealant (waterproof sealing material) from being scraped off and becoming thin when the connector housing is installed by replenishing with the waterproof sealing material applied to the replenishment inclined surface part, consideration is not given to curbing overflow of the sealant at the three-way junction of the sealant. 
     An object of the present invention is to provide an electronic control unit that curbs overflow of a sealant at a three-way junction of the sealant in the vicinity of a connector. 
     Solution to Problem 
     In order to achieve the above object, an electronic control unit of the present invention is an electronic control unit including: a base member that has a recessed part on an outer periphery and an accommodation space for an electronic circuit board formed inside the recessed part; a cover member that covers the electronic circuit board and is attached to the base member; a connector housing that has a connector and is at least partially accommodated between the base member and the cover member; a first seal part that is provided in the recessed part and seals between the base member and the cover member; a second seal part that is provided in the recessed part and seals between the base member and the connector housing; and a third seal part that is connected to the first seal part and the second seal part and seals between the cover member and the connector housing, in which a space part connected to the recessed part and recessed further from a surface forming the recessed part is formed in a part where the first seal part, the second seal part, and the third seal part intersect. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to curb overflow of a sealant at a three-way junction of the sealant in the vicinity of a connector of an electronic control unit. 
     Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective view illustrating an appearance according to an embodiment of an electronic control unit of the present invention. 
         FIG.  2    is a development (exploded three-dimensional view) of the electronic control unit of  FIG.  1   . 
         FIG.  3    is a schematic view illustrating an application locus of a sealant according to a first embodiment of the present invention. 
         FIG.  4 A  is a diagram schematically illustrating a seal structure part in a three-way junction according to the first embodiment of the present invention, and is a plan view of the seal structure part as viewed from above. 
         FIG.  4 B  is a cross-sectional view schematically illustrating a cross section taken along line IVB-IVB of  FIG.  4 A . 
         FIG.  4 C  is a cross-sectional view schematically illustrating a cross section taken along line IVC-IVC of  FIG.  4 A . 
         FIG.  5 A  is a diagram schematically illustrating a seal structure part in a three-way junction according to a second embodiment of the present invention, and is a plan view of the seal structure part as viewed from above. 
         FIG.  5 B  is a cross-sectional view schematically illustrating a cross section taken along line VB-VB of  FIG.  5 A . 
         FIG.  5 C  is a cross-sectional view schematically illustrating a cross section taken along line VC-VC of  FIG.  5 A . 
         FIG.  6 A  is a diagram schematically illustrating a seal structure part in a three-way junction according to a third embodiment of the present invention, and is a cross-sectional view of the seal structure part (VIA-VIA cross-sectional view of  FIG.  6 B ). 
         FIG.  6 B  is a cross-sectional view schematically illustrating a cross section taken along line VIB-VIB of  FIG.  6 A . 
         FIG.  7 A  is a diagram schematically illustrating a seal structure part in a three-way junction according to a fourth embodiment of the present invention, and is a cross-sectional view of the seal structure part (VIIA-VIIA cross-sectional view of  FIG.  7 B ). 
         FIG.  7 B  is a cross-sectional view schematically illustrating a cross section taken along line VIIB-VIIB of  FIG.  7 A . 
         FIG.  8    is a perspective view illustrating an appearance according to a modification of the electronic control unit of  FIG.  1   . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An electronic control unit according to the present invention has a waterproof structure and is particularly suitable for use in a vehicle. Hereinafter, an electronic control unit (ECU) mounted in an engine room will be described. 
     An embodiment of the electronic control unit according to the present invention will be described with reference to  FIGS.  1  to  3   .  FIG.  1    is a perspective view illustrating an appearance according to an embodiment of an electronic control unit  1  of the present invention.  FIG.  2    is a development (exploded three-dimensional view) of the electronic control unit  1  of  FIG.  1   .  FIG.  3    is a schematic view illustrating an application locus of a sealant  50  according to a first embodiment of the present invention. 
     In the description of the present embodiment, a height direction H, a width direction W, and a depth direction D are defined based on  FIG.  2   . The height direction H is along the vertical direction (vertical direction), and the width direction W and the depth direction D are along the horizontal direction (lateral direction). In the description of the present embodiment, the vertical direction (vertical direction) and the horizontal direction (lateral direction) are defined on the basis of  FIG.  2   , and do not define directions in the mounted state of the electronic control unit  1 . 
     As illustrated in  FIGS.  1  and  2   , the electronic control unit  1  according to the present invention includes a connector  21  connected to a vehicle harness side, an electronic circuit board  60  on which an electronic component  61  is mounted, a cover (cover member)  30  and a base (base member)  40  for housing the connector  21  and the electronic circuit board  60 , and a sealing material  50  provided in a boundary part between the connector  21 , the cover  30 , and the base  40 . 
     The cover (cover member)  30  covers the electronic circuit board  60  and is attached to the base (base member)  40 . 
     The cover  30  has a substantially rectangular shape when viewed in the vertical direction, and includes a top surface  31  that is the highest surface of the electronic control unit  1  and three side walls  32 ,  33 , and  34  surrounding the electronic control unit  1 . The side walls  32 ,  33 , and  34  are continuously provided so as to surround three side surfaces of the electronic control unit  1 , the side wall  32  forms a side wall on the back surface side of the electronic control unit  1 , and the side walls  33  and  34  form side walls on both side surface sides in the width direction W of the electronic control unit  1 . 
     A front surface  30 F side of the cover  30  is open, and this open part is surrounded by a front edge  311  of the top surface  31  and front edges  331  and  341  of the side walls  33  and  34 . The front edge  311  of the top surface  31  is along the lateral direction, and the front edges  331  and  341  of the side walls  33  and  34  are along the height direction. Further, the front edges  331  and  341  are inclined so as to retract toward the back surface (side wall  32 ) side from the top surface  31  side toward the base  40  side. 
     The side walls  32 ,  33 , and  34  of the cover  30  are provided a flange parts  36  protruding laterally (laterally outward) in a position closer to the top surface  31  than a lower end part (lower edge part)  35  of the cover  30 . The flange part  36  is provided in the vicinity of the lower end part  35  of the cover  30 . 
     The cover  30  is formed of resin such as polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), and nylon (PA), or metal containing aluminum, iron, or the like as a main component. 
     A connector housing  20  has a front surface  201  substantially perpendicular to the top surface  31  of the cover  30 , and has a plurality of connectors  21  on the front surface  201 . Side surfaces  203  and  204  of the connector housing  20  have a substantially trapezoidal shape. Therefore, a rear part  202  of the connector housing  20  is inclined so as to protrude toward the back surface (side wall  32 ) side from the upper surface side toward the lower surface side. 
     The connector housing  20  is inclined such that the rear part  202  extends along the inclination of the front edges  331  and  341  of the side walls  33  and  34  of the cover  30 , and is fitted to the open part of the front surface  30 F of the cover  30  when the cover  30  is assembled. 
     In addition, the connector housing  20  has a protruding part  23  protruding downward (toward base  40 ) in a lower surface part thereof. The protruding part  23  is provided inside the front surface  201  and the side surfaces  203  and  204  along the front surface  201  and the side surfaces  203  and  204 . 
     The connector housing  20  has the connector  21 , and at least a part of the connector housing  20  is accommodated between the base member  40  and the cover member  30 . In this case, the front surface  201  and both side surfaces  203  and  204  of the connector housing  20  are exposed to the outside of the base member  40  and the cover member  30 . 
     The connector housing  20  including the connector  21  is formed of resin such as polybutylene terephthalate (PBT), polyamide (PA), or polyphenylene sulfide (PPS). That is, the connector  21  is integrally formed of the same resin material as that of the connector housing  20 . The connector  21  includes a plurality of connector terminals  211  made of metal containing copper as a main component. 
     The connector terminal  211  exchanges voltage and current between the electronic control unit  1  and an external device. The connector terminal  211  is electrically connected to the electronic circuit board  60  by soldering, press-fitting, or the like. 
     The electronic circuit board  60  is fixed to the connector housing  20  and integrated with the connector housing  20 . The connector  21  is formed of a right angle connector  21  whose connection direction is parallel to a board surface of the electronic circuit board  60  (mounting surface of electronic component  61 ). 
     The connector housing  20  has a seal groove  22 . The seal groove  22  includes a seal groove part (connector upper seal groove part)  221  formed on the upper side of the connector  21  and seal groove parts (connector side seal groove parts)  222  and  223  formed in both end parts (both side parts) in the width direction W of the connector housing  20 . The seal groove parts  222  and  223  are formed so as to connect an upper part and a lower part of the connector housing  20 , and are inclined so as to protrude rearward (toward back surface  32 ) from the upper part side to the lower part side of the connector housing  20 . That is, the seal groove parts  222  and  223  are inclined along the inclination of the front edges  331  and  341  of the side surfaces  33  and  34  of the cover  30 . 
     The seal groove part (connector upper seal groove part)  221  and the seal groove parts (connector side seal groove parts)  222  and  223  form one communicating seal groove  22 . 
     The base  40  has four sides  401 ,  402 ,  403 , and  404 , and has a substantially rectangular shape when viewed in the vertical direction. The side  401  forms a side on the front surface side. The side  402  forms a side on the back surface side. The sides  403  and  404  form sides on both sides in the width direction W. The base  40  includes a plurality of mounting brackets  42  protruding laterally (outward in width direction W) from the sides  403  and  404 . 
     The base (base member)  40  has a seal groove (recessed part)  41  on the outer periphery thereof, and an accommodation space (bottom surface part)  43  of the electronic circuit board  60  is formed inside the seal groove  41 . 
     The seal groove  41  is formed along the four sides  401 ,  402 ,  403 , and  404  of the base  40  so as to surround the central bottom surface part  43  of the base  40 . The seal groove  41  includes a seal groove part  411  formed along the side  401 , a seal groove part  412  formed along the side  402 , a seal groove part  413  formed along the side  403 , and a seal groove part  414  formed along the side  404 . The four seal groove parts  411 ,  412 ,  413 , and  414  form one communicating seal groove  41 . 
     The base  40  is formed of resin such as polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), and nylon (PA), or metal containing aluminum, iron, or the like as a main component. 
     The connector housing  20  has a seal structure part including the seal groove  22  ( 221 ,  222 , and  223 ) and the protruding part  23 . The cover  30  has a seal structure part including an inner surface part along the front edge  311  of the top surface  31 , the front edges  331  and  341  of the side walls  33  and  34  of the cover  30 , and the lower end part (lower edge)  35  of the cover  30 . The base  40  has a seal structure part formed of the seal groove  41  ( 411 ,  412 ,  413 , and  414 ). 
     As illustrated in  FIG.  2   , when the connector housing  20  and the base  40  are assembled, the protruding part  23  of the connector housing  20  is inserted into the seal groove parts  411 ,  413 , and  414  of the seal groove  41  of the base  40 , whereby the seal structure part of the connector housing  20  and the seal structure part of the base  40  are combined. When the connector housing  20  and the cover  30  are assembled, the front edges  331  and  341  of the side walls  33  and  34  of the cover  30  are inserted into the seal groove parts  222  and  223  of the seal groove  22  of the connector housing  20 , and the inner surface part along the front edge  311  of the top surface  31  faces the seal groove part  221 , whereby the seal structure part of the connector housing  20  and the seal structure part of the cover  30  are combined. When the cover  30  and the base  40  are assembled, the lower end part (lower edge)  35  of the cover  30  is inserted into the seal groove parts  412 ,  413 , and  414  of the seal groove  41  of the base  40 , whereby the seal structure part of the cover  30  and the seal structure part of the base  40  are combined. In this case, the waterproof property of the electronic control unit  1  is secured by applying the sealant forming the sealing material  50  to each seal structure part. 
     As illustrated in  FIGS.  2  and  3   , the sealing material  50  includes three seal parts of a first seal part (outer peripheral seal part)  51  for waterproofing between the cover  30  other than the connector part and the base, and a second seal part (connector lower seal part)  52  and a third seal part (connector upper seal part)  53  for waterproofing the periphery of the connector housing  20 . 
     That is, the first seal part  51  is provided in the recessed part  41  and seals between the base member  40  and the cover member  30 . In addition, the second seal part  52  is provided in the recessed part  41  and seals between the base member  40  and the connector housing  20 . Further, the third seal part  53  is connected to the first seal part  51  and the second seal part  52  to seal between the cover member  30  and the connector housing  20 . 
     A three-way junction (intersection)  50 J of the sealing material  50  is formed in a part where the three seal parts  51 ,  52 , and  53  intersect. 
     In the present embodiment, the electronic control unit  1  has a rectangular shape when viewed in the vertical direction H, and parts (three-way junctions)  50 J where the first seal part  51 , the second seal part  52 , and the third seal part  53  intersect are provided on two surfaces on both sides of the surface on which the connector  21  is mounted among the four side surfaces of the outer periphery of the electronic control unit  1 . These two surfaces are surfaces corresponding to the sides  403  and  404  of the base  40 . 
     The sealing material  50  is formed by applying a liquid sealant to the seal groove  41  and then solidifying the sealant. In the description of the present specification, reference numeral  50  may be used for a sealing material (seal part), and reference numeral  50  may also be used for a liquid sealant. 
     The seal groove  41  has a function of holding the sealant. The first seal part  51  and the second seal part  52  are formed in the seal groove part  41 , and the third seal part  53  is formed in the seal groove  22 . A three-way junction (intersection)  41 J of the seal grooves  22  and  41  is formed in a part where the seal groove  22  intersects with the seal groove part  41 . The three-way junction  50 J of the sealing material  50  is formed in the three-way junction  41 J of the seal grooves  22  and  41 . 
     The three-way junction (intersection)  41 J of the seal grooves  22  and  41  is formed in the seal groove part  413  and the seal groove part  414 . The first seal part  51  is formed across the seal groove part  412 , the seal groove part  413 , and the seal groove part  414 . In this case, the first seal part  51  is formed in a part of the seal groove part  413  and the seal groove part  414  on the back surface side (seal groove part  412  side) of the three-way junction  41 J. The second seal part  52  is formed across the seal groove part  411 , the seal groove part  413 , and the seal groove part  414 . The second seal part  52  is formed in a part of the seal groove part  413  and the seal groove part  414  on the front surface side (seal groove part  411  side) of the three-way junction  41 J. 
     At the three-way junction  41 J of the seal grooves  22  and  41 , twice or more application of the sealant cannot be avoided due to the application locus of the sealant, so that the application amount becomes excessive and an overflow amount of the sealant after assembly of the cover  30  increases. In addition, since the three-way junction  41 J of the seal grooves  22  and  41  is an application start point or end point when the sealant forming the second seal part  52  is applied, the sealant applied from a nozzle is not stable, and it is difficult to adjust the application amount. Therefore, a seal structure that curbs overflow of the sealant is required. 
     Furthermore, the three-way junction  41 J of the seal grooves  22  and  41  is a part where the connector housing  20 , the cover  30 , and the base  40  intersect, and is a part where high stress is generated in the sealing material  50  when a twisting force is applied to the connector  21  when the mating connector is inserted into and removed from the connector  21 . Therefore, if the application amount is reduced, the reliability of the seal part may be lowered. 
     In the following description, while “three-way junction” is referred to as the three-way junction (intersection)  50 J of the sealing material  50 , “three-way junction  50 J” can be regarded as the same as “three-way junction  41 J” of the seal grooves  22  and  41  unless inconsistent with the context. 
     The first seal part  51  is formed of a sealant applied to an outer peripheral part of the electronic control unit  1 . The second seal part  52  is formed of a sealant applied to the outer peripheral part of the electronic control unit  1 , and forms a seal part between the lower surface of the connector housing  20  and the bus  40 . The third seal part  53  is formed of a sealant applied to an upper surface side of the connector housing  20 , and forms a planar seal between the upper surface of the connector housing  20  and an inner surface part (plane) along the front edge  311  of the top surface  31 . Note that a protruding part may be provided on the inner surface part along the front edge  311  of the top surface  31 , and the protruding part may be inserted into the seal groove part  221  of the seal groove  22  of the connector housing  20 . 
     The first seal part  51 , the second seal part  52 , and the third seal part  53  will be described in more detail with reference to  FIGS.  2  and  3   . 
     Among the first seal part  51 , the second seal part  52 , and the third seal part  53  forming the sealing material  50 , the third seal part (connector upper seal part)  53  and the first seal part (outer peripheral seal part)  51  are formed after forming the second seal part (connector lower seal part)  52 . 
     As a method of forming the second seal part  52 , first, the sealant is applied to the seal groove part  412 , the seal groove part  413 , and the seal groove part  414  corresponding to the connector lower seal part  52  of the base  40 , and then the electronic circuit board  60  on which the connector housing  20  is mounted is assembled to the base  40 . At this time, by pushing and spreading the sealant while crushing the sealant on the lower surface (lower seal surface) of the connector housing  20  and the protruding part  23 , a gap in the seal grooves  412 ,  413 , and  414  is filled with the sealant, and the second seal part  52  is formed. 
     In this case, both end parts of the second seal part  52  are located at the three-way junction  50 J of the sealing materials  51 ,  52 , and  53 , and are located at the three-way junction  41 J of the seal groove  22  ( 222  and  223 ) and the seal groove  41  ( 413  and  414 ). 
     As the third seal part  53  and the first seal part  51 , first, the sealant is applied to the seal groove part  221  on the upper surface part of the connector housing  20  assembled when the second seal part  52  is formed. In addition, the connector housing  20  has the seal groove parts  222  and  223  that descend from the upper surface of the connector housing  20  toward both end parts of the second seal part  52  on both side parts in the width direction W, and the sealant is also applied to the seal groove parts  222  and  223 . 
     Therefore, the third seal part  53  includes an upper surface seal part  531  and side seal parts (inclined seal parts)  533  and  534 . As illustrated in  FIG.  2   , the sealant is applied so that both end parts  533 A and  534 A of the side seal parts  533  and  534  of the third seal part  53  merge with both end parts of the second seal part  52  at the three-way junction  41 J between the seal groove  22  and the seal groove  41 . 
     In addition, from the merging position of the second seal part  52  and the third seal part  53 , the sealant is also applied to the outer peripheral part of the base  40  where the second seal part  52  is not formed, and the first seal part  51  is formed. After the sealant of the first seal part  51  is applied, when the cover  30  is assembled to the base  40 , the sealant is pushed and spread while being crushed by the seal structure part of the cover  30 , whereby the gap in the seal grooves  22 ,  412 ,  413 , and  414  is filled with the sealant, and the third seal part  53  and the first seal part  51  are formed. 
     When the application locus of the sealant forming the seal parts  51 ,  52 , and  53  is illustrated, the application locus has a shape as illustrated in  FIG.  3   . In addition, the seal parts  51 ,  52 , and  53  in  FIG.  3    represent the shape of the sealing material formed by solidification of the sealant. 
     The three-way junction  50 J is an intersection point of seal parts where the three seal parts  51 ,  52 , and  53  overlap, and since a plurality of sealants forming the seal parts  51 ,  52 , and  53  overlap, the application amount of the sealant increases. In addition, since the three-way junction  50 J is a place which is a starting point or an ending point of the application of the second seal part  52  applied to the lower part of the connector, the application control of the sealant is not stable, and the application amount increases. Therefore, at the three-way junction  50 J, an overflow amount of the sealant  50  from the seal groove after the connector housing  20 , the cover  30 , and the base  40  are assembled increases. 
     The sealant  50  is formed of a material such as a silicon-based material, an epoxy-based material, or a urethane-based material, and serves as an adhesive. 
     Hereinafter, embodiments of the seal structure part according to the present invention will be described. 
     First Embodiment 
     A first embodiment of the seal structure part of the present embodiment will be described with reference to  FIGS.  4 A to  4 C . 
       FIG.  4 A  is a diagram schematically illustrating a seal structure part in a three-way junction  50 J according to the first embodiment of the present invention, and is a plan view of the seal structure part as viewed from above.  FIG.  4 B  is a cross-sectional view schematically illustrating a cross section taken along line IVB-IVB of  FIG.  4 A .  FIG.  4 C  is a cross-sectional view schematically illustrating a cross section taken along line IVC-IVC of  FIG.  4 A . Configurations similar to those in the above-described embodiment are denoted by the same reference numerals as those in the above-described embodiment, and redundant description will be omitted. Hereinafter, configurations different from those in the above-described embodiment will be described. 
     A seal groove (recessed part)  41  ( 413  and  414 ) of the present embodiment has a recessed part (first recessed part)  41 JA 1  in which a bottom surface of the seal groove  41  of a base  40  is recessed downward from bottom surface parts of other seal groove  41  parts in a three-way junction  50 J. The first recessed part  41 JA 1  forms a space part (first space part) recessed further from a surface forming the seal groove (recessed part)  41 , and forms a groove expansion part (first groove expansion part) expanding the internal space of the seal groove  41 . In the present embodiment, the first recessed part  41 JA 1  expands the seal groove  41  in the depth direction (height direction). The first recessed part  41 JA 1  is formed on a bottom surface of the seal grooves  413  and  414  and is located on an extension line of seal grooves  222  and  223 . 
     A sealant  50  enters the first recessed part  41 JA 1  to form a seal expansion part (first seal expansion part)  50 JA 1 . 
     In the present embodiment, the seal groove (recessed part)  41  is formed in the base  40  so as to be recessed in the thickness direction (height direction H) of the base  40 . Then, the first recessed part (space part)  41 JA 1  is formed in the base  40  so as to be recessed deeper than the recessed part  41  in the thickness direction of the base  40 . In this case, the first recessed part (space part)  41 JA 1  is preferably formed only in an inner part of the recessed part  41  of the base  40  so as to be recessed deeper than the recessed part  41  in the thickness direction of the base  40 . As a result, an excessive sealant can be absorbed without increasing the width of the seal groove  41 , and the width dimension of an electronic control unit  1  can be reduced. 
     In the present embodiment, when the amount of the sealant  50  is excessive, the first recessed part  41 JA 1  serves as a relief part of the excessive sealant, and the first recessed part  41 JA 1  absorbs the excessive sealant. This curbs overflow of the sealant  50  to the outside of the electronic control unit  1 . 
     In addition, in the present embodiment, it is possible to increase the application amount of the sealant  50  in the seal groove  41  at a three-way junction  50 J. When a connector  21  is twisted when a mating connector is inserted into and removed from the connector  21 , the highest stress is generated in the three-way junction  50 J. By increasing the application amount of the sealing material  50  of the three-way junction  50 J, the stress generated in the three-way junction  50 J can be reduced. 
     Further, in the present embodiment, a protruding part  352  to be inserted into the first recessed part  41 JA 1  is provided at a lower end part  35  of side walls  32  and  34  of a cover  30 . As a result, in the three-way junction  50 J, the bonding area between the cover  30  and the base  40  by the sealant  50  is increased, and the bonding strength can be improved. 
     In addition, in the present embodiment, the protruding part  352  is formed such that a seal thickness T 2  formed between the bottom surface of the seal groove  41  and the tip end (lower end) of the protruding part  352  is larger than a seal thickness T 1  of other parts, so that the excessive sealant can be more reliably absorbed. 
     That is, in the configuration including the protruding part  352 , the electronic control unit  1  is configured as follows. The seal groove (recessed part)  41  is formed in the base  40  so as to be recessed in the thickness direction of the base  40 . The first recessed part (space part)  41 JA 1  is formed in the base  40  so as to be recessed deeper than the recessed part  41  in the thickness direction of the base  40 . The cover  30  includes cover main bodies  31 ,  32 ,  33 , and  34  covering an electronic circuit board  60 , and an insertion part  35  inserted into the recessed part  41 . The insertion part  35  includes the protruding part  352  to be inserted into the space part  41 JA 1 . 
     It is also possible to not provide the protruding part  352 , and form the lower end part  35  of the side walls  32  and  34  of the cover  30  linearly as indicated by a dotted line IL 1 . 
     Second Embodiment 
     A second embodiment of the seal structure part of the present embodiment will be described with reference to  FIGS.  5 A to  5 C . 
       FIG.  5 A  is a diagram schematically illustrating a seal structure part in a three-way junction  50 J according to the second embodiment of the present invention, and is a plan view of the seal structure part as viewed from above.  FIG.  5 B  is a cross-sectional view schematically illustrating a cross section taken along line VB-VB of  FIG.  5 A .  FIG.  5 C  is a cross-sectional view schematically illustrating a cross section taken along line VC-VC of  FIG.  5 A . Configurations similar to those in the above-described embodiment are denoted by the same reference numerals as those in the above-described embodiment, and redundant description will be omitted. Hereinafter, configurations different from those in the above-described embodiment will be described. 
     A seal groove  41  ( 413  and  414 ) of the present embodiment has a recessed part (second recessed part)  41 JA 2  in which an inner side wall (inner side surface) of the seal groove  41  is recessed in a horizontal direction (lateral direction) toward the inside of an electronic control unit  1  at a three-way junction  50 J. The second recessed part  41 JA 2  forms a space part (second space part) recessed further from a surface forming the seal groove (recessed part)  41 , and forms a groove expansion part (second groove expansion part) expanding the seal groove  41  in a groove width direction (lateral direction). In addition, the second recessed part  41 JA 2  forms an enlarged width part that enlarges the seal groove  41  in the groove width direction. 
     In the present embodiment, a bottom surface of the second recessed part  41 JA 2  is configured to have the same depth as bottom surface parts of other seal groove  41  parts. The second recessed part  41 JA 2  is formed on an inner side surface of the seal grooves  413  and  414 , and an extension line of seal grooves  222  and  223  is located on the side of an intersecting position where the extension line intersects with the seal groove  41  ( 413  and  414 ). 
     In the present embodiment, the seal groove (recessed part)  41  is formed in the base  40  so as to be recessed in the thickness direction of the base  40 . Then, the second recessed part (space part)  41 JA 2  is formed in the base  40  so as to be recessed from the inner side surface of the recessed part  41  toward the inside of the base  40 . 
     In the present embodiment, in addition to the first recessed part  41 JA 1 , the second recessed part  41 JA 2  serves as a relief part for an excessive sealant, and the second recessed part  41 JA 2  also absorbs the excessive sealant. In this case, the volume of the relief part of the excessive sealant can be increased. The sealant  50  enters the second recessed part  41 JA 2  to form a seal expansion part (second seal expansion part)  50 JA 2 . 
     In the present embodiment, the second recessed part  41 JA 2  is provided together with the first recessed part  41 JA 1  of the first embodiment. However, the structure may omit the first recessed part  41 JA 1 . In this case, too, the second recessed part  41 JA 2  can form a relief part of the excessive sealant. Further, by making the bottom surface of the second recessed part  41 JA 2  the same depth as bottom surface parts of other seal groove  41  parts, a space in the height direction of the electronic control unit  1  is not required, and the dimension (thickness) in the height direction of the electronic control unit  1  can be reduced. 
     Note that as indicated by a dotted line IL 2  in  FIG.  5 C , the bottom surface of the second recessed part  41 JA 2  may be configured to have the same depth as the depth of the bottom surface of the first recessed part  41 JA 1 , so that the volume of the relief part of the excessive sealant becomes larger. 
     Third Embodiment 
     A third embodiment of the seal structure part of the present embodiment will be described with reference to  FIGS.  6 A and  6 B . 
       FIG.  6 A  is a diagram schematically illustrating a seal structure part in a three-way junction  50 J according to the third embodiment of the present invention, and is a cross-sectional view of the seal structure part (VIA-VIA cross-sectional view of  FIG.  6 B ).  FIG.  6 B  is a cross-sectional view schematically illustrating a cross section taken along line VIB-VIB of  FIG.  6 A . Configurations similar to those in the above-described embodiment are denoted by the same reference numerals as those in the above-described embodiment, and redundant description will be omitted. Hereinafter, configurations different from those in the above-described embodiment will be described. 
     In the present embodiment, a lower end part (lower edge part)  35  of side walls  32  and  34  of a cover  30 , which is inserted into a seal groove  41  at a three-way junction  50 J, has a third recessed part  41 JA 3  having a structure in which the thickness is partially reduced. The third recessed part  41 JA 3  forms a groove expansion part (third groove expansion part) that expands the seal groove  41  in a groove width direction (lateral direction). That is, the third recessed part  41 JA 3  is formed by a thin part  351  formed in the lower end part  35  of the side walls  32  and  34  of the cover  30  at the three-way junction  50 J. The thin part  351  enlarges a space in the seal groove  41 . 
     In the present embodiment, the third recessed part  41 JA 3  is provided in addition to the first recessed part  41 JA 1  of the first embodiment. The third recessed part  41 JA 3 , together with the first recessed part  41 JA 1 , serves as a relief part for an excessive sealant, and the third recessed part  41 JA 3  also absorbs the excessive sealant. In this case, the volume of the relief part of the excessive sealant can be increased. The sealant  50  enters the third recessed part  41 JA 3  to form a seal expansion part (third seal expansion part)  50 JA 3 . 
     In the present embodiment, the excessive sealant can be absorbed without increasing the width of the seal groove  41 , and the width dimension of an electronic control unit  1  can be reduced. 
     The third recessed part  41 JA 3  of the present embodiment is provided together with the first recessed part  41 JA 1  of the first embodiment. However, the structure may omit the first recessed part  41 JA 1 . In this case, too, the third recessed part  41 JA 3  can form a relief part for an excessive sealant. 
     In addition, the third recessed part  41 JA 3  of the present embodiment may be formed together with the second recessed part  41 JA 2  of the second embodiment as long as the width dimension of the electronic control unit  1  is not a problem. In this case, the configuration may include all of the third recessed part  41 JA 3 , the second recessed part  41 JA 2 , and the first recessed part  41 JA 1 . In addition, in this case, the configurations described in the first and second embodiments described above can be appropriately adopted as the depth of the seal groove  41  in the first recessed part  41 JA 1  and the second recessed part  41 JA 2 . 
     Fourth Embodiment 
     A fourth embodiment of the seal structure part of the present embodiment will be described with reference to  FIGS.  7 A and  7 B . 
       FIG.  7 A  is a diagram schematically illustrating a seal structure part in a three-way junction  50 J according to the fourth embodiment of the present invention, and is a cross-sectional view of the seal structure part (VIIA-VIIA cross-sectional view of  FIG.  7 B ).  FIG.  7 B  is a cross-sectional view schematically illustrating a cross section taken along line VIIB-VIIB of  FIG.  7 A . Configurations similar to those in the above-described embodiment are denoted by the same reference numerals as those in the above-described embodiment, and redundant description will be omitted. Hereinafter, configurations different from those in the above-described embodiment will be described. 
     The present embodiment has a structure in which the first recessed part  41 JA 1  of the first embodiment is disposed in a position shifted from a position immediately below a lower end part (seal structure part)  35  of side walls  32  and  34  of a cover  30  toward the inside of an electronic control unit  1  in a seal groove  41 . 
     As in the first embodiment, a sealant  50  enters the first recessed part  41 JA 1  to form a seal expansion part  50 JA 1 . 
     In the present embodiment, when the sealant  50  is applied to the seal groove  41  and the cover  30  is assembled, the sealant  50  can be crushed by the lower end part  35  of the side walls  32  and  34  of the cover  30  and a bottom surface of the seal groove  41 . That is, as compared with the case where the first recessed part  41 JA 1  is formed in the entire groove width of the seal groove  41  as in the first embodiment, the interval between the lower end part  35  of the side walls  32  and  34  of the cover  30  and the bottom surface of the seal groove  41  is narrowed, and the effect of crushing the sealant  50  by the lower end part  35  of the side walls  32  and  34  is improved. As a result, in the present embodiment, the property of filling the seal groove  41  with the sealant  50  is improved. 
     Fifth Embodiment 
     A fifth embodiment in which the configuration of an electronic control unit  1  is changed will be described with reference to  FIG.  8   .  FIG.  8    is a perspective view illustrating an appearance according to a modification of the electronic control unit  1  of  FIG.  1   . Configurations similar to those in the above-described embodiment are denoted by the same reference numerals as those in the above-described embodiment, and redundant description will be omitted. Hereinafter, configurations different from those in the above-described embodiment will be described. 
     The electronic control unit  1  of the present embodiment has, on both side surfaces, fixing parts  70  of a cover  30  in addition to mounting brackets  42  for a vehicle. 
     That is, the electronic control unit  1  includes the mounting bracket  42  for the vehicle in the vicinity of a part (three-way junction)  50 J where a first seal part  51 , a second seal part  52 , and a third seal part  53  intersect. In addition, the electronic control unit  1  includes the fixing part  70  for fixing the cover  30  to a base  40  in the vicinity of the part (three-way junction)  50 J where the first seal part  51 , the second seal part  52 , and the third seal part intersect. 
     In the electronic control unit  1 , when an overflow amount of a sealant  50  at the three-way junction  50 J increases, the overflowed sealant  50  adheres to the mounting bracket  42  and the fixing part  70  of the cover  30 . In such a case, the overflowed sealant may interfere with a fixing tool when attaching the electronic control unit  1  to the vehicle, or fixing of the fixing part  70  may be hindered, for example. 
     These problems can be improved by applying the first recessed part  41 JA 1 , the second recessed part  41 JA 2 , and the third recessed part  41 JA 3  of each embodiment described above. 
     In addition, in each of the above-described embodiments, the description has been given assuming that the first recessed part  41 JA 1 , the second recessed part  41 JA 2 , and the third recessed part  41 JA 3  are provided in both of the two three-way junctions  50 J. However, it is also possible to apply the present invention to at least one of the three-way junctions  50 J. 
     The electronic control unit  1  according to each of the above-described embodiments has one of the following configurations (1) and (2). 
     (1) An electronic control unit includes: a base member  40  that has a recessed part (seal groove)  41  on an outer periphery and an accommodation space for an electronic circuit board  60  formed inside the recessed part  41 ; a cover member  30  that covers the electronic circuit board  60  and is attached to the base member  40 ; a connector housing  20  that has a connector  21  and is at least partially accommodated between the base member  40  and the cover member  30 ; a first seal part  51  that is provided in the recessed part  41  and seals between the base member  40  and the cover member  30 ; a second seal part  52  that is provided in the recessed part  41  and seals between the base member  40  and the connector housing  20 ; and a third seal part  53  that is connected to the first seal part  51  and the second seal part  52  and seals between the cover member  30  and the connector housing  20 , in which a space part connected to the recessed part  41  and recessed further from a surface forming the recessed part  41  is formed in a part (three-way junction)  50 J where the first seal part  51 , the second seal part  52 , and the third seal part  53  intersect. 
     Here, the space part includes at least one of a first recessed part  41 JA 1  and a second recessed part  41 JA 2 . 
     (2) An electronic control unit includes: a base member  40  that has a recessed part (seal groove)  41  on an outer periphery and an accommodation space for an electronic circuit board  60  formed inside the recessed part  41 ; a cover member  30  that covers the electronic circuit board  60  and is attached to the base member  40 ; a connector housing  20  that has a connector  21  and is at least partially accommodated between the base member  40  and the cover member  30 ; a first seal part  51  that is provided in the recessed part  41  and seals between the base member  40  and the cover member  30 ; a second seal part  52  that is provided in the recessed part  41  and seals between the base member  40  and the connector housing  20 ; and a third seal part  53  that is connected to the first seal part  51  and the second seal part  52  and seals between the cover member  30  and the connector housing  20 , in which the recessed part  41  is formed in the base member  40  so as to be recessed in a thickness direction of the base member  40 , the cover member  30  includes cover main bodies  31 ,  32 ,  33 , and  34  covering the electronic circuit board  60 , and an insertion part  35  inserted into the recessed part  41 , and in a part where the first seal part  51 , the second seal part  52 , and the third seal part  53  intersect, expansion parts (space parts)  41 JA 1 ,  41 JA 2 , and  41 JA 3  expanding an internal space of the recessed part  41  are formed by reducing the thickness of the insertion part  35 , forming the recessed part  41  to be low in the depth direction, or forming an inner side surface of the recessed part  41  so as to be recessed toward the inside of the base member  40 . 
     In this case, the part including the space parts  41 JA 1  and  41 JA 2  recessed further from the surface forming the recessed part  41  is provided in at least one location. In addition, the part including the expansion parts  41 JA 1 ,  41 JA 2 , and  41 JA 3  is provided in at least one location. 
     The space parts  41 JA 1 ,  41 JA 2 , and  41 JA 3  form an excessive sealant accommodation part that accommodates an excess of the sealant  50  that fills the recessed part  41 . In addition, the part including the space parts  41 JA 1  and  41 JA 2  recessed further from the surface forming the seal groove (recessed part)  41 , and the part including the space part (expansion part)  41 JA 3  expanding the internal space of the seal groove (recessed part)  41  are provided in at least one location. 
     In the present embodiment, the first recessed part  41 JA 1 , the second recessed part  41 JA 2 , and the third recessed part  41 JA 3  are provided to form a relief part for an excessive sealant. Therefore, the first recessed part  41 JA 1 , the second recessed part  41 JA 2 , and the third recessed part  41 JA 3  are disposed in the vicinity of a part (three-way junction)  50 J where the first seal part  51 , the second seal part  52 , and the third seal part  53  intersect. In this case, “vicinity” means within a range where an excessive liquid sealant can flow into each of the recessed parts  41 JA 1 ,  41 JA 2 , and  41 JA 3 . 
     Note that the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above embodiments have been described in detail for the sake of clarity of the present invention, and are not necessarily limited to the embodiments including all of the described configurations. In addition, a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of a different embodiment can be added to the configuration of a certain embodiment. In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment. 
     REFERENCE SIGNS LIST 
     
         
           1  electronic control unit 
           21  connector 
           30  cover 
           31  top surface of cover  30  (cover main body) 
           32 ,  33 ,  34  side surface of cover  30  (cover main body) 
           35  insertion part of cover  30  inserted into recessed part  41   
           352  protruding part 
           40  base 
           403 ,  404  two sides of base  40   
           41  seal groove (recessed part) 
           41 JA 1  first recessed part (space part) 
           41 JA 2  second recessed part (space part) 
           41 JA 3  third recessed part (space part) 
           42  mounting bracket 
           50  sealing material (seal part) 
           50 J three-way junction of seal member 
           51  first seal part 
           52  second seal part 
           53  third seal part 
           60  electronic circuit board 
           70  fixing part for fixing cover  30  to base  40