Patent Publication Number: US-2023163582-A1

Title: In-vehicle electric component-internal circuit unit

Description:
TECHNICAL FIELD 
     The present disclosure relates to an in-vehicle electric component-internal circuit unit that is housed inside a housing of an in-vehicle electric component. 
     BACKGROUND ART 
     Patent Document 1 discloses a structure in which, together with a battery module, a battery control system, etc., circuit units such as a junction box are housed inside a housing of a battery pack that is an in-vehicle electric component to be installed in a vehicle. Here, in order to enable the circuit units housed inside the battery-pack housing to be connected to external devices, a structure is adopted in which connectors to which external mating connectors are to be connected are provided on a peripheral wall of the housing, and the connectors and the circuit units are conductively connected using coated wires and bus bars. 
     CITATION LIST 
     Patent Documents 
     
         
         Patent Document 1: JP 2012-243449A 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In the structure disclosed in Patent Document 1, work for connecting the circuit units and the connectors provided on the housing needs to be performed when the circuit units are attached to the battery pack. Thus, there was a problem that the number of battery-pack-side work processes was increased. Furthermore, a space for carrying out the connection work is necessary between the circuit units and the connectors provided on the housing, and battery-pack size was increased in proportion to the space. 
     In view of this, disclosed is an in-vehicle electric component-internal circuit unit having a novel structure that can reduce the number of in-vehicle electric component-side work processes and reduce in-vehicle electric component size. 
     Solution to Problem 
     An in-vehicle electric component-internal circuit unit according to the present disclosure includes: an insulative holder that holds a circuit member; a wire harness that includes a coated wire, a circuit-side connection portion that is provided on an end portion on one side of the coated wire and connected to the circuit member, a connector that is provided on an end portion on the other side of the coated wire, and a cylindrical grommet through which the coated wire passes; a plate wall portion for covering a housing through-hole provided in a housing of an in-vehicle electric component; and an annular seal member that is provided on a first surface, which is a surface of the plate wall portion to be attached to the housing, and that comes into contact with the rim of the housing through-hole, wherein the wire harness passes through a grommet attachment hole that is provided so as to extend through the plate wall portion in a plate thickness direction, and the grommet attachment hole is sealed due to the grommet of the wire harness being in close contact with the grommet attachment hole. 
     Advantageous Effects of Invention 
     According to the present disclosure, an in-vehicle electric component-internal circuit unit having a novel structure that can reduce the number of in-vehicle electric component-side work processes and reduce in-vehicle electric component size can be provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is an overall perspective view illustrating a state in which an in-vehicle electric component-internal circuit unit according to embodiment 1 is housed inside a housing of an in-vehicle electric component. 
         FIG.  2    is an exploded perspective view corresponding to  FIG.  1   . 
         FIG.  3    is an exploded enlarged perspective view of the in-vehicle electric component-internal circuit unit illustrated in  FIG.  2   . 
         FIG.  4    is an enlarged view of a Iv-Iv cross-section in  FIG.  1   . 
         FIG.  5    is a diagram schematically illustrating an electrical configuration of the in-vehicle electric component-internal circuit unit in a path from a power source to a load. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Description of Embodiments of Present Disclosure 
     First, aspects of embodiment of the present disclosure will be listed and described. 
     An in-vehicle electric component-internal circuit unit according to the present disclosure is 
     (1) an in-vehicle electric component-internal circuit unit including: an insulative holder that holds a circuit member; a wire harness that includes a coated wire, a circuit-side connection portion that is provided on an end portion on one side of the coated wire and connected to the circuit member, a connector that is provided on an end portion on the other side of the coated wire, and a cylindrical grommet through which the coated wire passes; a plate wall portion for covering a housing through-hole provided in a housing of an in-vehicle electric component; and an annular seal member that is provided on a first surface, which is a surface of the plate wall portion to be attached to the housing, and that comes into contact with the rim of the housing through-hole, wherein the wire harness passes through a grommet attachment hole that is provided so as to extend through the plate wall portion in a plate thickness direction, and the grommet attachment hole is sealed due to the grommet of the wire harness being in close contact with the grommet attachment hole. 
     According to the in-vehicle electric component-internal circuit unit according to the present disclosure, the connector, which used to be provided on the housing of the in-vehicle electric component in the conventional structure, is provided on the end portion on the other side of the wire harness connected to the circuit member held by the holder. Furthermore, the plate wall portion for covering the housing through-hole provided in the housing of the in-vehicle electric component is attached, via the grommet, to the wire harness connected to the circuit member. As a result, the connector, which used to be provided on the housing of the in-vehicle electric component in the conventional structure, can be connected in advance to the circuit member as a constituent member of the in-vehicle electric component-internal circuit unit. Thus, the work for connecting a circuit unit and a connector provided on a housing, which used to be necessary in the conventional structure, is unnecessary, and the number of in-vehicle electric component-side work processes is reduced. As a result, a space for carrying out the connection work does not need to be secured between the housing and the circuit unit, and in-vehicle electric component size can also be reduced. 
     Furthermore, the housing through-hole provided in the in-vehicle electric component can be closed by covering the housing through-hole using the plate wall portion attached to the wire harness. The annular seal member, which is provided on the first surface of the plate wall portion to be attached to the housing and which comes into contact with the rim of the housing through-hole, is provided, and the grommet attachment hole provided in the plate wall portion is sealed due to the grommet being in close contact with the grommet attachment hole. Thus, waterproofness of the housing through-hole can be maintained. Here, because the plate wall portion is an in-vehicle electric component-internal circuit unit-side component that is provided separately from the housing of the in-vehicle electric component, the material for the plate wall portion can be selected more flexibly without restriction by the material of the housing. Thus, for example, a material that can advantageously realize the state of close contact between the grommet and the grommet attachment hole can also be selected as desired. In particular, because the volume of the plate wall portion is small compared to that of the entire housing, a better material for the plate wall portion can be selected while suppressing an increase in cost. 
     In addition, the annular seal member forms a so-called face seal that is sandwiched between the opposing surfaces of the rim of the housing through-hole and the plate wall portion. Thus, allowable assembly errors of the plate wall portion in two directions that are orthogonal to the direction in which the plate wall portion is attached to the housing can also be absorbed by the flexural deformation of the seal member. Note that the plate wall portion may be placed over the housing through-hole from inside the housing or from outside the housing. 
     Furthermore, in the conventional structure, there were also cases where, depending on the situation, it was necessary to provide an openable/closable opening in the housing of the in-vehicle electric component to carry out the work for connecting a connector and a circuit unit. According to the structure according to the present disclosure, such a structure is also unnecessary because the in-vehicle electric component-internal circuit unit is provided in advance with the connector connected to the circuit member. 
     (2) The plate wall portion is preferably made of metal. This is because the deformation of the plate wall portion itself is suppressed and the close contact between the grommet and the grommet attachment hole can be maintained even more advantageously, and waterproofness can thus be advantageously ensured. 
     (3) The first surface of the plate wall portion preferably is a surface facing the circuit-side connection portion. Because the first surface is a surface facing the circuit-side connection portion, the plate wall portion can be attached to the housing from outside the housing. Thus, a large work space can be secured, and work efficiency can be improved. Note that, in a case in which the plate wall portion is placed over and attached to the housing from outside the housing, it suffices to pass the wire harness through the grommet insertion hole of the plate wall portion to place the grommet in close contact with the grommet attachment hole after the plate wall portion has been attached to the housing. 
     (4) Preferably, a base plate portion on which the holder is mounted and fixed is further included. This is because the circuit member held by the holder can be stably supported due to the holder being mounted on a base member, and thus the durability of the entire circuit unit can be improved. 
     (5) The base plate portion is preferably provided with a support leg portion that protrudes downward from the base plate portion. Because the base plate portion is provided with the support leg portion, the circuit unit can be mounted above another component housed inside the in-vehicle electric component. Furthermore, the height position of the plate wall portion relative to the housing through-hole can be adjusted easily by changing the protruding length of the support leg portion, and thus an in-vehicle electric component-internal circuit unit with high versatility that can be applied to housing through-holes provided at various height positions can be provided. 
     (6) The base plate portion is preferably formed using a material that has higher thermal conductivity than the holder. Because the base plate portion is formed using a material that has higher thermal conductivity than the holder, heat transmitted to the holder from the circuit member, which includes heat-generating components such as a relay and a fuse, can be dissipated via a base member. 
     Details of Embodiments of Present Disclosure 
     A specific example of the in-vehicle electric component-internal circuit unit according to the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to such examples, but defined in the claims, and is intended to include all modifications within the meaning and the scope equivalent thereof. 
     Embodiment 1 
     Embodiment 1 of the present disclosure will be described below with reference to  FIGS.  1  to  5   . An in-vehicle electric component-internal circuit unit  10  is installed in a vehicle (not illustrated) such as an electric automobile or a hybrid automobile, for example. The in-vehicle electric component-internal circuit unit  10  supplies power from a power source  12  such as a battery to a load  14  such as a motor, and performs control relating thereto (see  FIG.  5   ). Note that, while the in-vehicle electric component-internal circuit unit  10  may be oriented in any direction, in the following description, the Z direction is regarded as the upward direction, the Y direction is regarded as the width direction, and the X direction is regarded as the longitudinally front direction. Furthermore, when more than one of a given member is provided, the reference sign therefor may be provided to only some of the members and may be omitted for the rest. 
     &lt;Schematic Circuit Configuration of In-vehicle Electric Component-Internal Circuit Unit  10 &gt; 
     As illustrated in  FIG.  5   , the in-vehicle electric component-internal circuit unit  10  includes an in-vehicle electric component-internal circuit unit  10   a  provided on the positive electrode side and an in-vehicle electric component-internal circuit unit  10   b  provided on the negative electrode side. A positive electrode side of the power source  12  is connected to an input side of the in-vehicle electric component-internal circuit unit  10   a , and a negative electrode side of the power source  12  is connected to an input side of the in-vehicle electric component-internal circuit unit  10   b . A positive electrode side of the load  14  is connected to an output side of the in-vehicle electric component-internal circuit unit  10   a , and a negative electrode side of the load  14  is connected to an output side of the in-vehicle electric component-internal circuit unit  10   b . A relay  16  that connects the power source  12  to the load  14  is connected between the input and output sides of each of the in-vehicle electric component-internal circuit units  10   a  and  10   b.    
     In addition, a precharge circuit  22 , in which a precharge resistance  18  and a precharge relay  20  are connected in series so that the relay  16  is bypassed, is connected to the relay  16  connecting the positive electrode sides of the power source  12  and the load  14 . Note that, in embodiment 1 of the present disclosure, the precharge resistance  18  is connected to an input side of the precharge relay  20 , as illustrated in  FIG.  5   . Note that, while a precharge circuit  22  is similarly connected also to the relay  16  connecting the negative electrode sides of the power source  12  and the load  14 , in embodiment 1 of the present disclosure, illustration of the p recharge circuit  22  connected to the relay  16  connecting the negative electrode sides of the power source  12  and the load  14  is omitted from the drawings to facilitate understanding. Furthermore, both the relay  16  and the precharge relay  20  are relays in which a contact portion is switched on and off by the contact portion being moved in accordance with the conduction state of an excitation coil, and both are controlled on and off by a control circuit inside a power distribution component  154  provided inside a later-described in-vehicle electric component  146 . As mentioned up to this point, the in-vehicle electric component-internal circuit units  10   a  and  10   b  are provided with substantially the same structure. 
     &lt;In-Vehicle Electric Component-Internal Circuit Unit  10 &gt; 
     For example, as illustrated in  FIG.  3   , the in-vehicle electric component-internal circuit unit  10  includes a lower case  24  that is positioned lower and an upper case  26  that is positioned higher when the in-vehicle electric component-internal circuit unit  10  is installed in a vehicle, and an insulative holder  28  is constituted by the lower case  24  and the upper case  26 . Furthermore, the in-vehicle electric component-internal circuit unit  10  includes a base plate portion  30  on which the holder  28  is mounted and fixed. The base plate portion  30  has the shape of a rectangular flat plate, and is formed by die-casting or press-punching, for example. Furthermore, the in-vehicle electric component-internal circuit unit  10  includes a plate wall portion  32  for covering a housing through-hole  180  provided in a housing  152  of the later-described in-vehicle electric component  146 . The plate wall portion  32  has the shape of a rectangular flat plate, and is formed by die-casting or press-punching, for example. As described above, the base plate portion  30  and the plate wall portion  32  are formed using a metal such as aluminum or an aluminum alloy. In addition, the in-vehicle electric component-internal circuit unit  10  includes a wire harness  34  for connecting the output sides of the in-vehicle electric component-internal circuit unit  10   a  and the in-vehicle electric component-internal circuit unit  10   a  to the load  14 . 
     &lt;Holder  28 &gt; 
     In a state in which the lower case  24  and the upper case  26  constituting the holder  28  are attached to one another, unillustrated bus bars for connecting the relays  16  and the precharge circuits  22 , unillustrated bus bars for establishing connection inside the precharge circuits  22 , etc., are housed inside the holder  28 . Furthermore, as illustrated in  FIGS.  2  and  3   , the two relays  16 , and bus bars  38  and  40  that are connected to connection portions  36   a  and  36   b  of each of the relays  16  are held by the holder  28  formed by attaching the lower case  24  and the upper case  26  to one another. 
     &lt;Lower Case  24 &gt; 
     The lower case  24  is formed by injection molding an insulative synthetic resin into a predetermined shape. For example, as illustrated in  FIG.  3   , the lower case  24  has the overall shape of a flat rectangular box. As illustrated in  FIG.  3   , the lower case  24  is open upward, and the four corners of the lower case  24  are cut out in the shape of quadrants. 
     &lt;Upper Case  26 &gt; 
     The upper case  26  is formed by injection molding an insulative synthetic resin into a predetermined shape. For example, as illustrated in  FIG.  3   , the upper case  26  has the overall shape of a flat rectangular box. The upper case  26  is open downward, and bolt insertion holes  42  are formed in the four corners of the upper case  26 . As illustrated in  FIG.  3   , two bus-bar-fixing cylinder portions  46  each having the shape of a circular cylinder are formed so as to protrude upward on each of the two longitudinal-direction end portions of a top surface  44  of the upper case  26 . The two bus-bar-fixing cylinder portions  46  are disposed so as to be separated from one another in the width direction. A bolt hole  48  that is open upward is provided in the upper surface of each bus-bar-fixing cylinder portion  46 . Furthermore, six relay-fixing cylinder portions  50  each having the shape of a circular cylinder are formed so as to protrude upward on the longitudinal-direction center portion of the top surface  44  of the upper case  26 . A bolt hole  52  that is open upward is provided in the upper surfaces of these relay-fixing cylinder portions  50 . Furthermore, on the rearward side of the top surface  44  of the upper case  26 , precharge-resistance mounting portions  54  that house the precharge resistances  18  and precharge relay mounting portions  56  that house the precharge relays  20  are provided so as to be open upward. 
     &lt;Relays  16 &gt; 
     The relays  16  are mechanical relays, and are controlled on and off by the control circuit provided inside the power distribution component  154  of the later-described in-vehicle electric component  146 . As illustrated in  FIG.  3   , the relays  16  each include a block-shaped relay main body  58 , the pair of annular connection portions  36   a  and  36   b , and a plurality of (three in the present embodiment) leg portions  60 . The leg portions  60  are each formed so as to protrude outward in the shape of a flat plate. The leg portions  60  each have a bolt insertion hole  62  extending therethrough in the vertical direction. 
     &lt;Bus Bars  38  and  40 &gt; 
     Each pair of the bus bars  38  and  40  is formed by machining metal plate materials that have electroconductivity. For example, as illustrated in  FIG.  3   , the bus bars  38  and  40  each have a crank shape. End portions on one side of the bus bars  38  and  40  are connected to the connection portions  36   a  and  36   b  of the relays  16 . End portions  39  on the other side of the bus bars  38  are connected to circuit-side connection portions  104  provided on end portions on one side of coated wires  102  constituting the later-described wire harness  34 . End portions  41  on the other side of the bus bars  40  constitute the input sides of the in-vehicle electric component-internal circuit unit  10 , and the positive electrode side and the negative electrode side of the power source  12  are connected thereto. Specifically, as described later, the end portions  41  on the other side of the bus bars  40  are connected to a wire harness  172  that is inserted into the housing  152  of the in-vehicle electric component  146  through a wire-harness insertion hole  168  provided in the housing  152  of the in-vehicle electric component  146 , as described later, and is connected to the power source  12  (see  FIG.  2   ). Note that the wire harness  172  is attached to the wire-harness insertion hole  168  via a grommet  170 , for example, and waterproofness is thus ensured. Furthermore, the wire harness  172  is also connected to the later-described power distribution component  154 . 
     &lt;Base Plate Portion  30 &gt; 
     As illustrated in  FIGS.  2  and  3   , the in-vehicle electric component-internal circuit unit  10  includes the base plate portion  30 , which has the shape of a rectangular flat plate. On the four corners of a top surface  64  of the base plate portion  30 , case-fixing cylinder portions  66  each having the shape of a circular cylinder are formed so as to protrude upward. A bolt hole  68  that is open upward is provided in the protruding end surfaces of the case-fixing cylinder portions  66 . In addition, in each of the peripheral edge portions of the top surface  64  of the base plate portion  30  facing one another in the width direction, two bolt insertion holes  70  are formed so as to be separated from one another in the longitudinal direction and so as to extend through the base plate portion  30  in the plate thickness direction. Furthermore, the base plate portion  30  is provided with a support leg portion  72 . 
     &lt;Support Leg Portion  72 &gt; 
     As illustrated in  FIG.  2   , the support leg portion  72  has the shape of a gutter that is open downward and that extends in the width direction (Y direction), and is formed by injection molding an insulative synthetic resin into a predetermined shape. The support leg portion  72  includes a top wall  74  that has the shape of a rectangular flat plate, and a pair of side walls  76  and  76  that protrude downward from the two longitudinal-direction (X-direction) end portions of the top wall  74 . Bolt insertion holes  78  are provided so as to extend through the four corners of the top wall  74 . In each of the pair of side walls  76  and  76 , a support-leg-portion flange portion  80  that extends in the longitudinal direction from the protruding end portion toward the direction separating from the opposite side wall  76  is formed. In each support-leg-portion flange portion  80 , bolt insertion holes  82  are formed so as to extend through the support-leg-portion flange portion  80  at three positions that are separated from one another in the width direction (Y direction). 
     &lt;Plate Wall Portion  32 &gt; 
     As illustrated in  FIGS.  2  and  3   , the in-vehicle electric component-internal circuit unit  10  includes the plate wall portion  32 , which has the shape of a rectangular flat plate. The plate wall portion  32  includes a first surface  84  that is the surface to be placed over and attached to the housing  152  of the later-described in-vehicle electric component  146  and that is positioned toward the rear in  FIG.  2   , and a second surface  86  that is the surface on the opposite side to the first surface  84  and that is positioned toward the front in  FIG.  2   . 
     As illustrated in  FIG.  3   , bolt insertion holes  88  are provided so as to extend through the four corners of the first surface  84  of the plate wall portion  32 . Furthermore, a plate-wall through-hole  90  that has a rectangular cross-sectional shape and that extends through the plate wall portion  32  in the plate thickness direction (front-rear direction) is formed in the center portion of the plate wall portion  32 . A cylindrical portion  92  that has the shape of a cylinder protruding toward the front over the entire circumference is provided on the rim portion of the plate-wall through-hole  90 . Furthermore, a flange portion  94  that extends inward is formed on the protruding end portion of the cylindrical portion  92 , and a grommet attachment hole  96  that has a circular cross-sectional shape and that extends through the flange portion  94  in the plate thickness direction (front-rear direction) is formed in the center portion of the flange portion  94 . 
     In addition, as illustrated in  FIGS.  3  and  4   , a seal-member-housing groove portion  98  that has a rectangular cross-sectional shape and that extends over the entire circumference along the rim portion of the plate wall portion  32  is formed in the first surface  84  of the plate wall portion  32 . An annular seal member  100  made of rubber is housed inside the seal-member-housing groove portion  98 . 
     &lt;Wire Harness  34 &gt; 
     As illustrated in  FIG.  3   , the wire harness  34  includes two coated wires  102 , and circuit-side connection portions  104  that are provided on end portions on one side (rear end portions in  FIG.  3   ) of the coated wires  102  and that are connected to the bus bars  38  constituting circuit members. Furthermore, the wire harness  34  includes a connector  106  that is provided on end portions on the other side (front end portions in  FIG.  3   ) of the coated wires  102 , and a cylindrical grommet  108  through which the coated wires  102  pass. 
     &lt;Coated Wires  102 , Circuit-Side Connection Portions  104 &gt; 
     As illustrated in  FIGS.  3  and  4   , the coated wires  102  each include a core wire  110  and an insulating coating  112  that covers the core wire  110 . Specifically, the coated wires  102  each have a structure in which the core wire  110 , which is constituted by a plurality of metal element wires made from a conductor such as copper or aluminum, is covered by the electrically-insulative insulating coating  112 , which is made of an ethylene-based resin, a styrene-based resin, or the like. As illustrated in  FIG.  3   , in the end portion on one side of each coated wire  102 , the insulating coating  112  is stripped to expose the core wire  110 , and a core-wire crimping portion  116  of a crimp terminal  114  is crimped and connected to the exposed core wire  110 . Thus, the circuit-side connection portions  104 , which are constituted by tab-shaped connection portions of the crimp terminals  114 , are provided on the end portions on one side of the coated wires  102 . Furthermore, as illustrated in  FIG.  4   , the insulating coating  112  is stripped to expose the core wire  110  in the end portion on the other side of each coated wire  102 , and an external-side connection portion  118  is formed by a metal plate-shaped member being connected to the exposed core wire  110  using a known technique such as welding. 
     &lt;Connector  106 &gt; 
     As illustrated in  FIGS.  3  and  4   , the connector  106  includes a connector housing  120  that is made of a synthetic resin. The connector housing  120  has the shape of a rectangular box that is open toward the front. Furthermore, the connector housing  120  is provided with a cylindrical portion  124  that protrudes in the shape of a circular cylinder toward the rear from the rim portion of a bottom wall  122  of the connector housing  120 . In addition, vertically-elongated slit-shaped external-side-connection-portion insertion holes  126  are formed in the bottom wall  122  of the connector housing  120  so as to extend through the bottom wall  122  in the plate thickness direction (see  FIG.  4   ). Furthermore, the connector  106  is provided on the end portions on the other side of the coated wires  102  by the external-side connection portions  118  being pushed into the external-side-connection-portion insertion holes  126  of the connector housing  120 . 
     &lt;Grommet  108 &gt; 
     As illustrated in  FIGS.  3  and  4   , the grommet  108 , through which the coated wires  102  extend, includes a wire insertion portion  128  having the shape of a circular cylinder in each of the two longitudinal-direction (X-direction) end portions thereof, and is formed integrally using a rubber material such as ethylene propylene rubber (EPDM), chloroprene rubber (CR), or silicone rubber (SI). A bellows portion  130  and a large-diameter cylinder portion  132  are provided between the pair of wire insertion portions  128  and  128  provided in the two end portions. The bellows portion  130  has the structure of a bellows-shaped hollow cylinder. Specifically, in the bellows portion  130 , annularly-extending mountain portions  134  and valley portions  136  are connected alternately in the longitudinal direction (see  FIG.  4   ), and thus the bellows portion  130  can be stretched in the longitudinal direction and also can be bent in directions (Y and Z directions) that are orthogonal to the longitudinal direction. 
     An annular groove portion  138  that has a rectangular cross-sectional shape and that extends over the entire circumference is formed in the outer circumferential surface of the large-diameter cylinder portion  132  so that the grommet  108  is fixed to the plate wall portion  32  by the annular groove portion  138  being fitted into the inner edge portion of the grommet attachment hole  96  formed in the plate wall portion  32 . The large-diameter cylinder portion  132  is connected to the bellows portion  130  via a diameter-increasing cylinder portion  140 . The diameter-increasing cylinder portion  140  is formed so that the diameter thereof increases from the bellows portion  130  toward the large-diameter cylinder portion  132 . Furthermore, the large-diameter cylinder portion  132  is connected, via a diameter-decreasing cylinder portion  142 , to the wire insertion portion  128  provided in the rear end portion of the grommet  108 . The diameter-decreasing cylinder portion  142  is formed so that the diameter thereof decreases from the large-diameter cylinder portion  132  toward the wire insertion portion  128 . Furthermore, by connecting a wire insertion portion  128 , the bellows portion  130 , the diameter-increasing cylinder portion  140 , the large-diameter cylinder portion  132 , the diameter-decreasing cylinder portion  142 , and a wire insertion portion  128  in order from the front side, a coated-wire insertion hole  144  through which the coated wires  102  are passed is formed in the inner surface of the grommet  108  so as to be open in the front-rear direction. 
     &lt;In-Vehicle Electric Component  146 &gt; 
     The in-vehicle electric component  146  illustrated in  FIGS.  1  and  2    is installed in a vehicle (not illustrated) such as an electric automobile or a hybrid automobile, for example. For example, as illustrated in  FIG.  2   , the in-vehicle electric component  146  includes a lower cover  148  that is positioned lower and an upper cover  150  that is positioned higher when the in-vehicle electric component  146  is installed in a vehicle, and an insulative housing  152  is constituted by the lower cover  148  and the upper cover  150 . Furthermore, in the in-vehicle electric component  146 , the power distribution component  154 , which includes the control circuit, etc., is housed inside the housing  152 . 
     &lt;Lower Cover  148 &gt; 
     As illustrated in  FIG.  2   , the lower cover  148  is formed by injection molding an insulative synthetic resin into a predetermined shape. The lower cover  148  has the shape of a rectangular box, and is open upward. The lower cover  148  includes a lower-cover flange portion  156  that extends outward in the horizontal direction (width direction and longitudinal direction) over the entire circumference from the opening rim portion. In the lower-cover flange portion  156 , a plurality of (twenty in the present embodiment) bolt insertion holes  158  extending through the lower-cover flange portion  156  in the plate thickness direction are provided so as to be separated from one another in the circumferential direction. The bolt insertion holes  158  are formed so as to also extend into lower-cover-fixing cylinder portions  160  that have the shape of a circular cylinder and that protrude downward from the lower surface of the lower-cover flange portion  156 . In addition, six support-leg-portion-fixing cylinder portions  164  are provided so as to protrude upward on a bottom surface  162  of the lower cover  148 . Furthermore, in a peripheral wall  166  on one width-direction (Y-direction) side of the lower cover  148 , the wire-harness insertion hole  168  having a circular cross-sectional shape is formed so as to extend through the peripheral wall  166  in the plate thickness direction. The rubber grommet  170  having the shape of a circular cylinder is fitted into the wire-harness insertion hole  168 , and the wire harness  172  is inserted into the housing  152  via a through-hole provided in the center of the grommet  170 . Power, etc., is supplied to the in-vehicle electric component-internal circuit unit  10  and the power distribution component  154  of the in-vehicle electric component  146  via the wire harness  172 . Furthermore, the entry of water from between the wire-harness insertion hole  168  and the wire harness  172  is prevented by the grommet  170 . 
     &lt;Upper Cover  150 , Housing Through-Hole  180 &gt; 
     The upper cover  150  is formed by injection molding an insulative synthetic resin into a predetermined shape. The upper cover  150  has the shape of a rectangular box, and is open downward. The upper cover  150  includes an upper-cover flange portion  174  that extends outward in the horizontal direction (width direction and longitudinal direction) over the entire circumference from the opening rim portion. In the upper-cover flange portion  174 , a plurality of (twenty in the present embodiment) bolt insertion holes  176  extending through the upper-cover flange portion  174  in the plate thickness direction are provided so as to be separated from one another in the circumferential direction. Furthermore, in a peripheral wall  178  on the longitudinally front-direction (X-direction) side of the upper cover  150 , a housing through-hole  180  that has a horizontally-elongated rectangular cross-sectional shape is formed so as to extend through the peripheral wall  178  in the plate thickness direction. Bolt insertion holes  182  are provided near the four corners of the rim portion of the housing through-hole  180  so as to extend through the rim portion. 
     &lt;Assembly Process of In-Vehicle Electric Component-Internal Circuit Unit  10 &gt; 
     Subsequently, an example of an assembly process of the in-vehicle electric component-internal circuit unit  10  will be described. The assembly process of the in-vehicle electric component-internal circuit unit  10  is not limited to that disclosed below. 
     First, the lower case  24  and the upper case  26  constituting the holder  28  are prepared. Next, the assembly of the holder  28  is completed by attaching the lower case  24  and the upper case  26  to one another in a state in which the unillustrated bus bars for connecting the relays  16  and the precharge circuits  22 , the unillustrated bus bars for establishing connection inside the precharge circuit  22 , etc., are housed inside the holder  28 . Subsequently, the precharge resistances  18  and the precharge relays  20  are respectively housed from above into the precharge-resistance mounting portions  54  and the precharge-relay mounting portions  56  provided on the holder  28 . In addition, the leg portions  60  of the relays  16  are placed on and fastened using bolts to the relay-fixing cylinder portions  50  provided on the holder  28 . Furthermore, the end portions on one side of the bus bars  38  and  40  are connected to the connection portions  36   a  and  36   b  of the relays  16  by being fastened using bolts, and the end portions  39  and  41  on the other side of the bus bars  38  and  40  are placed on the bus-bar-fixing cylinder portions  46  provided on the holder  28 . Then, the end portions  39  on the other side of the bus bars  38  are fixed to bus-bar-fixing cylinder portions  46  by being fastened using bolts together with the circuit-side connection portions  104  provided to the crimp terminals  114  of the wire harness  34  as described later. Furthermore, the end portions  41  on the other side of the bus bars  40  are fixed to bus-bar-fixing cylinder portions  46  by being fastened using bolts together with connection members provided to the unillustrated wire harness connected to the power source  12 . As a result of the above, circuit members are constituted by the precharge resistances  18  and the precharge relays  20  for forming the precharge circuits  22 , the relays  16 , the various bus bars housed inside the holder  28 , etc. Furthermore, these circuit members are held by the insulative holder  28 . 
     Next, the base plate portion  30  is prepared. Then, the bolt insertion holes  42  provided in the four corners of the holder  28  are mounted on and fixed to the bolt holes  68  of the case-fixing cylinder portions  66  provided on the base plate portion  30  by being fastened using bolts. Thus, the holder  28  is fixed onto the base plate portion  30 . Note that the base plate portion  30  is formed using aluminum or an aluminum alloy, and the holder  28  is made of a synthetic resin. In other words, the base plate portion  30  is formed using a material having higher thermal conductivity than the holder  28 . Thus, heat transmitted to the holder  28  from the circuit members, which include heat-generating components such as the relays  16  and fuses, can be dissipated via the base plate portion  30 . 
     Subsequently, the base plate portion  30  having the holder  28  mounted and fixed thereon is mounted on the top wall  74  of the support leg portion  72  from above. The bolt insertion holes  70  provided in the base plate portion  30  and the bolt insertion holes  78  provided in the top wall  74  of the support leg portion  72  are positioned relative to one another, and are then fixed to one another by being fastened using bolts. As a result of this, the base plate portion  30  is provided with the support leg portion  72 , which protrudes downward (in the opposite direction from the Z-direction arrow) from the base plate portion  30 . 
     Next, the wire harness  34  is prepared. Specifically, the two coated wires  102  are prepared first. Then, in the end portion on one side (the rear end portion in  FIG.  3   ) of each coated wire  102 , the insulating coating  112  is stripped to expose the core wire  110 , and the core-wire crimping portion  116  of a crimp terminal  114  is crimped to the exposed core wire  110 . Thus, the circuit-side connection portions  104  constituted by the tab-shaped connection portions of the crimp terminals  114  are formed on the end portions on one side of the coated wires  102 . Furthermore, in the end portion on the other side (the front end portion in  FIG.  4   ) of each coated wire  102 , the insulating coating  112  is stripped to expose the core wire  110 , and a metal plate-shaped member is connected to the exposed core wire  110  using a known technique such as welding. Thus, the external-side connection portions  118  are formed. Next, the connector housing  120  is prepared, and the external-side connection portions  118  are pushed into the external-side-connection-portion insertion holes  126  of the connector housing  120 . Thus, the connector  106  including the external-side connection portions  118  is formed on the end portions on the other side of the coated wires  102 . 
     Subsequently, the grommet  108  is prepared. First, the coated wires  102  having been formed as described above are inserted into the coated-wire insertion hole  144  of the grommet  108  from the circuit-side connection portion  104  side, and the grommet  108  is arranged at a predetermined position on the coated wires  102 . As a result of the above, the assembly of the wire harness  34  is completed. Then, the circuit-side connection portions  104  provided in the wire harness  34  having been formed in such a manner are fastened using bolts to the end portions  39  on the other side of the bus bars  38  on the holder  28  having been formed as described above. Finally, the plate wall portion  32  is prepared. Thus, the in-vehicle electric component-internal circuit unit  10  in a state before the plate wall portion  32  is attached to the grommet  108  is prepared. 
     Next, the in-vehicle electric component-internal circuit unit  10  before the plate wall portion  32  is attached thereto is housed inside the housing  152  of the in-vehicle electric component  146 . Specifically, the power distribution component  154  is already housed inside the housing  152  of the in-vehicle electric component  146 . The support leg portion  72  provided in the in-vehicle electric component-internal circuit unit  10  is placed on the power distribution component  154  so as to cover the power distribution component  154  from above. Then, the bolt insertion holes  82  provided in the support-leg-portion flange portion  80  of the support leg portion  72  are mounted on the support-leg-portion-fixing cylinder portions  164  provided on the lower cover  148  of the housing  152  of the in-vehicle electric component  146 , and are then fixed by being fastened using bolts. 
     Subsequently, the upper cover  150  is used to cover the lower cover  148  of the in-vehicle electric component  146 , on which the in-vehicle electric component-internal circuit unit  10  before the plate wall portion  32  is attached thereto has been mounted. In doing so, the housing through-hole  180  provided in the upper cover  150  is covered in advance using the plate wall portion  32 . That is, the bolt insertion holes  88  provided in the plate wall portion  32  are placed over the bolt insertion holes  182  provided in the upper cover  150  from the outside, and are fastened to the bolt insertion holes  182  using bolts. Thus, the housing through-hole  180  provided in the upper cover  150  constituting the housing  152  of the in-vehicle electric component  146  is covered by the plate wall portion  32 . Here, as illustrated in  FIG.  4   , the annular seal member  100  coming into contact with the rim of the housing through-hole  180  is provided on the first surface  84  (the rear surface in  FIG.  4   ), which is the surface of the plate wall portion  32  to be attached to the upper cover  150  constituting the housing  152 . Furthermore, as illustrated in  FIG.  3   , the first surface  84  of the plate wall portion  32  is a surface facing the circuit-side connection portions  104 . Specifically, a surface facing the circuit-side connection portions  104  is a surface facing the circuit-side connection portions  104  in the X direction. 
     Finally, the upper cover  150  having the housing through-hole  180  covered by the plate wall portion  32  is used to cover the lower cover  148  of the in-vehicle electric component  146 , on which the in-vehicle electric component-internal circuit unit  10  before the plate wall portion  32  is attached thereto has been mounted. In doing so, first, the external-side connection portion  118  side of the wire harness  34  of the in-vehicle electric component-internal circuit unit  10  is passed through the housing through-hole  180  and the grommet attachment hole  96  from inside the upper cover  150 . In this state, the upper-cover flange portion  174  is placed over the lower-cover flange portion  156 . Subsequently, the inner edge portion of the grommet attachment hole  96  formed in the plate wall portion  32  is fitted into the annular groove portion  138  of the grommet  108  of the wire harness  34 . Then, the bolt insertion holes  176  in the upper-cover flange portion  174  are placed over and fastened using bolts to the bolt insertion holes  158  in the lower-cover flange portion  156 . As a result of this, the in-vehicle electric component-internal circuit unit  10  is housed and retained inside the housing  152  of the in-vehicle electric component  146 . Thus, as illustrated in  FIG.  4   , the wire harness  34  passes through the grommet attachment hole  96  provided so as to extend through the plate wall portion  32  in the plate thickness direction (the X direction in  FIG.  4   ). Moreover, because the grommet  108  constituting the wire harness  34  is in close contact with the grommet attachment hole  96 , the grommet attachment hole  96  is sealed by the grommet  108 . Furthermore, the annular seal member  100  is sandwiched between the plate wall portion  32  and the rim of the housing through-hole  180 . 
     According to the in-vehicle electric component-internal circuit unit  10  according to the present disclosure provided with such a structure, the connector, which conventionally used to be provided on the housing  152  of the in-vehicle electric component  146 , is provided on the end portion on the other side of the wire harness  34  constituting the in-vehicle electric component-internal circuit unit  10 . Moreover, the plate wall portion  32  covering the housing through-hole  180  provided in the housing  152  of the in-vehicle electric component  146  is attached, via the grommet  108 , to the wire harness  34  constituting the in-vehicle electric component-internal circuit unit  10 . Thus, the connector, which conventionally used to be provided on the housing  152  of the in-vehicle electric component  146 , can be configured as the connector  106  constituting the in-vehicle electric component-internal circuit unit  10 . Accordingly, the work for connecting the connector provided on the housing  152  and the in-vehicle electric component-internal circuit unit, which conventionally used to be necessary, is unnecessary, and the number of work processes is reduced. Moreover, a space for carrying out the connection work does not need to be secured between the housing  152  and the in-vehicle electric component-internal circuit unit, and thus the size of the in-vehicle electric component  146  can also be reduced. 
     Furthermore, the housing through-hole  180  provided in the housing  152  of the in-vehicle electric component  146  is covered by the plate wall portion  32 . Moreover, because the annular seal member  100 , which comes into contact with the rim of the housing through-hole  180 , is provided between the plate wall portion  32  and the housing  152 , the infiltration of water from a gap between the plate wall portion  32  and the housing  152  is prevented. Furthermore, because the grommet attachment hole  96  is sealed due to the grommet  108  constituting the wire harness  34  being in close contact with the grommet attachment hole  96 , the infiltration of water from a gap between the wire harness  34  and the grommet attachment hole  96  is also prevented. Note that, because the plate wall portion  32  is an in-vehicle electric component-internal circuit unit  10 -side component, the material for the plate wall portion  32  can be selected more flexibly without restriction by the material of the housing  152  of the in-vehicle electric component  146 . Thus, by forming the plate wall portion  32  from a metal (aluminum or an aluminum alloy in the present embodiment) as in the present embodiment, for example, the state of close contact between the grommet  108  and the grommet attachment hole  96  in the plate wall portion  32  can be advantageously realized, and waterproofness can thus be advantageously ensured. Moreover, because the plate wall portion  32  is small compared to the entire in-vehicle electric component  146 , a better material for the plate wall portion  32  can be selected while suppressing an increase in cost. 
     Furthermore, because the first surface  84 , which is the surface of the plate wall portion  32  to be attached to the upper cover  150  constituting the housing  152 , is a surface facing the circuit-side connection portions  104  of the wire harness  34 , the plate wall portion  32  can be attached from outside the upper cover  150 . Thus, a large work space can be secured, and work efficiency can be improved. 
     In addition, the annular seal member  100  forms a so-called face seal that is sandwiched between the opposing surfaces of the rim of the housing through-hole  180  and the plate wall portion  32 . Thus, allowable assembly errors of the plate wall portion  32  in two directions that are orthogonal to the direction in which the plate wall portion  32  is attached to the housing  152  can also be absorbed by the flexural deformation of the seal member  100 . 
     Furthermore, conventionally, there were also cases where it was necessary to provide an openable/closeable opening in the housing  152  of the in-vehicle electric component  146  in order to connect the connector  106  and the bus bars  38  constituting circuit members. However, according to the present embodiment, such an opening is also unnecessary because the in-vehicle electric component-internal circuit unit  10  is provided in advance with the connector  106  connected to the bus bars  38 . 
     Furthermore, because the in-vehicle electric component-internal circuit unit  10  includes the base plate portion  30 , on which the holder  28  is mounted and fixed, the circuit members held by the holder  28  can be stably supported, and thus the durability of the entire in-vehicle electric component-internal circuit unit  10  can be improved. 
     In addition, because the base plate portion  30  is provided with the support leg portion  72 , the in-vehicle electric component-internal circuit unit  10  can be mounted on the power distribution component  154  housed inside the in-vehicle electric component  146 , for example. Furthermore, the height position of the in-vehicle electric component-internal circuit unit  10  relative to the housing through-hole  180  can be adjusted easily by changing the protruding length of the side walls  76  of the support leg portion  72 . Thus, the in-vehicle electric component-internal circuit unit  10  can be applied to housing through-holes  180  provided at various height positions. 
     OTHER EMBODIMENTS 
     The technique disclosed in the present specification is not limited to the embodiment described based on the description above and the drawings, and embodiment such as those described below, for example, are also included in the technical scope of the technique disclosed in the present specification. 
     (1) In the present embodiment, the plate wall portion  32  is placed over the rim of the housing through-hole  180  from outside the housing  152 . However, there is no limitation to this. For example, the plate wall portion  32  may be placed over the rim of the housing through-hole  180  from inside the housing  152 . In this case, the plate wall portion  32  and the grommet  108  can be attached to one another before the in-vehicle electric component-internal circuit unit  10  is mounted on the housing  152 . 
     (2) In the present embodiment, description is provided while referring to an example of the in-vehicle electric component  146  in which the power distribution component  154  and the in-vehicle electric component-internal circuit unit  10  according to the present disclosure are housed inside the housing  152 . However, there is no limitation to this. For example, the in-vehicle electric component  146  may be a battery pack in which a battery is housed in place of the power distribution component  154 . In this case, the wire-harness insertion hole  168  need not be provided in the housing  152 . 
     (3) In the present embodiment, the support leg portion  72  is fixed to the bottom surface  162  of the housing  152 . However, there is no limitation to this. The support leg portion  72  may be fixed to any position of the housing  152 , such as the peripheral walls  178 . Furthermore, while the support leg portion  72  was separate from the base plate portion  30 , the support leg portion  72  may be formed integrally with the base plate portion  30  or may not be included. 
     LIST OF REFERENCE NUMERALS 
     
         
         
           
               10  In-vehicle electric component-internal circuit unit 
               10   a  In-vehicle electric component-internal circuit unit 
               10   b  In-vehicle electric component-internal circuit unit 
               12  Power source 
               14  Load 
               16  Relay 
               18  Precharge resistance 
               20  Precharge relay 
               22  Precharge circuit 
               24  Lower case 
               26  Upper case 
               28  Holder 
               30  Base plate portion 
               32  Plate wall portion 
               34  Wire harness 
               36   a  Connection portion 
               36   b  Connection portion 
               38  Bus bar 
               39  End portion on other side 
               40  Bus bar 
               41  End portion on other side 
               42  Bolt insertion hole 
               44  Top surface 
               46  Bus-bar-fixing cylinder portion 
               48  Bolt hole 
               50  Relay-fixing cylinder portion 
               52  Bolt hole 
               54  Precharge-resistance mounting portion 
               56  Precharge-relay mounting portion 
               58  Relay main body 
               60  Leg portion 
               62  Bolt insertion hole 
               64  Upper surface 
               66  Case-fixing cylinder portion 
               68  Bolt hole 
               70  Bolt insertion hole 
               72  Support leg portion 
               74  Top wall 
               76  Side wall 
               78  Bolt insertion hole 
               80  Support-leg-portion flange portion 
               82  Bolt insertion hole 
               84  First surface 
               86  Second surface 
               88  Bolt insertion hole 
               90  Plate-wall through-hole 
               92  Cylindrical portion 
               94  Flange portion 
               96  Grommet attachment hole 
               98  Seal-member-housing groove portion 
               100  Seal member 
               102  Coated wire 
               104  Circuit-side connection portion 
               106  Connector 
               108  Grommet 
               110  Core wire 
               112  Insulating coating 
               114  Crimp terminal 
               116  Core-wire crimping portion 
               118  External-side connection portion 
               120  Connector housing 
               122  Bottom wall 
               124  Cylindrical portion 
               126  External-side-connection-portion insertion hole 
               128  Wire insertion portion 
               130  Bellows portion 
               132  Large-diameter cylinder portion 
               134  Mountain portion 
               136  Valley portion 
               138  Annular groove portion 
               140  Diameter-increasing cylinder portion 
               142  Diameter-decreasing cylinder portion 
               144  Coated-wire insertion hole 
               146  In-vehicle electric component 
               148  Lower cover 
               150  Upper cover 
               152  Housing 
               154  Power distribution component 
               156  Lower-cover flange portion 
               158  Bolt insertion hole 
               160  Lower-cover-fixing cylinder portion 
               162  Bottom surface 
               164  Support-leg-portion-fixing cylinder portion 
               166  Peripheral wall 
               168  Wire-harness insertion hole 
               170  Grommet 
               172  Wire harness 
               174  Upper-cover flange portion 
               176  Bolt insertion hole 
               178  Peripheral wall 
               180  Housing through-hole 
               182  Bolt insertion hole