Patent Publication Number: US-2017353020-A1

Title: Circuit assembly and electrical junction box

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. national stage of PCT/JP2015/084121 filed Dec. 4, 2015, which claims priority of Japanese Patent Application No. JP 2014-258909 filed Dec. 22, 2014. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a circuit assembly and an electrical junction box. 
     BACKGROUND 
     Conventionally, circuit assemblies in which a circuit board and a heat discharging member that discharges heat of the circuit board to the outside are stacked on each other are known. In this type of circuit assemblies, the circuit board is adhered to the heat discharging member with an adhesive agent. JP 2005-151617A discloses a circuit assembly in which a sheet-shaped component obtained by braiding insolation fibers into a sheet is laid on an adhesive agent that is applied to a heat discharging member so that the adhesive agent passes substantially uniformly through the entire sheet-shaped component. A circuit structure is laid on this sheet-shaped component and is pressed towards the heat discharging member side, thus fixing it to the heat discharging member. 
     Meanwhile, in JP 2005-151617A in which the circuit structure is pressed towards the heat discharging member side when being fixed to the heat discharging plate, if the distance between a circuit board and the heat discharging member is not kept constant, there is a risk that the pressure that acts on the adhesive agent via the circuit structure when it is pressed may become non-uniform, and defects may occur such as locations where adhesion with the adhesive agent is insufficient. On the other hand, if a jig is used to keep the distance between the circuit board and the heat discharging member constant, there is the problem that a cost will be incurred for the jig. 
     JP 2014-82844A discloses an electrical junction box provided with a circuit unit on which electronic components are mounted, a heat discharging member that discharges heat of the circuit unit, and a frame-shaped member that is disposed on the heat discharging member and accommodates the circuit unit. The frame-shaped member has compartments into which the electronic components are accommodated, and holds the electronic components in their positions. 
     Here, if a spacer for keeping the distance between the circuit board and the heat discharging member constant is provided between the circuit structure and the heat discharging member in order to solve the problems of JP 2005-151617A, it is not preferable to provide, in addition to the spacer, a frame-shaped member for holding electronic components in positions as disclosed in JP 2014-82844A because this will lead to an increase in the number of components and complication of the structure. 
     The present invention was made in view of the above-described circumstances, and it is an object thereof to hold a part of a circuit unit at a predetermined position while keeping the distance between a circuit board and a heat discharging member constant, with a simple configuration. 
     SUMMARY 
     According to the present invention, a circuit assembly includes: a circuit unit that includes an electrically conducting path on which electronic components are mounted; a heat discharging member that is placed on the circuit unit, and is configured to discharge heat of the circuit unit; and a spacer that is disposed between the circuit unit and the heat discharging member, wherein the spacer is provided with a main portion that is disposed between the circuit unit and the heat discharging member, and an accommodating portion that accommodates a part of the circuit unit. 
     According to the present invention, since the main portion of the spacer is disposed between the circuit unit and the heat discharging member, it is possible to keep the distance between the circuit unit and the heat discharging member constant without using a jig. Furthermore, since the accommodating portion of the spacer accommodates a part of the circuit unit, it is possible to hold that part of the circuit unit at a predetermined position using the structure of the spacer, instead of providing a separate member for accommodating a part of the circuit unit. Accordingly, it is possible to hold a part of the circuit unit at a predetermined position while keeping the distance between the circuit board and the heat discharging member constant, with a simple configuration. 
     The embodiments of the present invention may have following aspects: 
     The main portion and the accommodating portion may be molded in one piece using a resin. 
     With this, it is possible to simplify the configuration compared to a case where, for example, a separate accommodating portion is fixed to the main portion to form a spacer. 
     The accommodating portion may accommodate an external connection terminal of the circuit unit. 
     The accommodating portion may accommodate a coil of the circuit unit. 
     The accommodating portion may accommodate a nut of the circuit unit. 
     The main portion may be provided with a through hole that is formed through the main portion, and a heat transmission portion that is arranged in the through hole, and is configured to transmit heat of the circuit unit to the heat discharging member. 
     With this, the heat transmission portion allows heat of the circuit unit to be discharged from the heat discharging member. 
     The circuit unit and the heat discharging member may be fastened to each other with screws. 
     With this, the circuit unit and the heat discharging member can be fixed to each other firmly with the screws, while the spacer receives a force acting when the circuit unit and the heat discharging member are fastened to each other with the screws. 
     An electrical junction box is provided with the above-described circuit assembly. 
     According to the present invention, it is possible to hold a part of a circuit unit at a predetermined position while keeping the distance between a circuit board and a heat discharging member constant, with a simple configuration. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating an electrical junction box according to Embodiment 1. 
         FIG. 2  is a plan view illustrating the electrical junction box. 
         FIG. 3  is a cross-sectional view taken along a line A-A in  FIG. 2 . 
         FIG. 4  is a cross-sectional view taken along a line B-B in  FIG. 2 . 
         FIG. 5  is a plan view illustrating a circuit board. 
         FIG. 6  is a perspective view illustrating a spacer. 
         FIG. 7  is a plan view illustrating the spacer. 
         FIG. 8  is a front view illustrating the spacer. 
         FIG. 9  is a side view illustrating the spacer. 
         FIG. 10  is a rear view illustrating the spacer. 
         FIG. 11  is a bottom view illustrating the spacer. 
         FIG. 12  is a plan view illustrating an auxiliary member. 
         FIG. 13  is a side view illustrating the auxiliary member. 
         FIG. 14  is a perspective view illustrating a heat discharging member. 
         FIG. 15  is a plan view illustrating the heat discharging member. 
         FIG. 16  is a plan view illustrating a state in which the spacer is mounted on the heat discharging member. 
         FIG. 17  is a plan view illustrating a state in which the circuit board is mounted starting from the state of  FIG. 16 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiment 1 
     Hereinafter, Embodiment 1 will be described with reference to  FIGS. 1 to 17 . 
     An electrical junction box  10  is arranged on, for example, an electric power supplying path between a power supply such as a battery of a vehicle, and loads including an in-car electric component, such as a lamp or a wiper, and a motor, and can be used, for example, for a DC-DC converter, an inverter, or the like. In the description below, “upward” and “downward” are based on the directions in  FIG. 3 . 
     Electrical Junction Box  10   
     As shown in  FIGS. 1 and 4 , the electrical junction box  10  is provided with a circuit assembly  20 , and a shield cover  11  that covers the upper side of the circuit assembly  20 . The shield cover  11  is made of plate-shaped metal such as aluminum that was subjected to a punching process and a bending process, or a casting process, and is provided with, at a lower end thereof, fixation pieces  12  that are bent in an L-shape. As a result of the fixation pieces  12  being fastened to boss parts  34  of a heat discharging member  28  with screws  13 , the shield cover  11  is connected to the ground via the heat discharging member  28 . An external connection part  15  is formed in a corner of the electrical junction box  10 . The external connection part  15  accommodates, in the inside of a box portion  16 , a stud bolt  56  for connecting to a terminal at a terminal end of an external electric wire that is not shown, the box portion  16  being made of a synthetic resin and being able to be opened and closed with a cover portion  16 A. 
     Circuit Assembly  20   
     As shown in  FIG. 3 , the circuit assembly  20  is provided with: a circuit unit  20 A; the heat discharging member  28  that is placed on the circuit unit  20 A and discharges heat of the circuit unit  20 A; and a spacer  40  that is disposed between the circuit unit  20 A and the heat discharging member  28 . 
     Circuit Unit  20 A 
     The circuit unit  20 A is provided with a circuit board  21  with an electrically conducting path, and electronic components  26  that are mounted on the electrically conducting path. The circuit board  21  is rectangular as shown in  FIG. 5 , and has, at positions close to the peripheral edge of the circuit board  21 , a plurality of screw holes  22  for screwing screws  48  and a plurality of positioning holes  23  for positioning the circuit board  21  with respect to the spacer  40 . The screw holes  22  and the positioning holes  23  are formed through the circuit board  21 . This circuit board  21  is made by adhering a printed board  21 A and a busbar board  21 B with each other using an adhesive member (such as an adhesive sheet or an adhesive agent, for example). The printed board  21 A is rectangular, and is obtained such that an electrically conducting path (not shown) made of a copper foil is formed on an insulating plate made of an insulating material using printed wiring. The busbar board  21 B is constituted by a plurality of busbars that are made of metal plate materials such as copper or a copper alloy that have a shape conforming to the shape of the electrically conducting path, and are arranged at intervals to each other. The busbar board  21 B includes, at its ends, connector terminals  24  (an example of an “external connection terminal”), a terminal portion  25 A that is connected to the stud bolt  56  (an example of the “external connection terminal”) that is a part of the circuit unit  20 A, and terminal portions  25 B that are connected to ends of a coil wire  27 B of a coil  27 . A part of the terminal portion  25 A is cut out for the stud bolt  56  to be inserted thereinto. The terminal portions  25 B are provided with passage holes  25 C for connecting the coil wire  27 B by bolting. 
     The electronic components  26  are mounted on the circuit board  21  as shown in  FIGS. 3 and 4 , and include a high heat-generating component such as a switching element (for example, an FET (Field Effect Transistor)), a resistor, or the coil  27 , and a low heat-generating component such as a capacitor that generates relatively less heat. The high heat-generating component has a main portion that generates heat, and a plurality of lead terminals that are drawn from the main portion. The lead terminals of the electronic components  26  are soldered to the electrically conducting path of the printed board  21 A, and the busbar board  21 B. 
     The coil  27  includes a magnetic material core  27 A and the coil wire  27 B. The coil wire  27 B is obtained by winding a flat rectangular copper wire that has a rectangular cross section in a so-called edgewise manner. The coil wire  27 B has, at the respective ends thereof, passage holes  27 C that are formed through the coil wire  27 B, and are electrically connected to the terminal portions  25 B by inserting the shaft portions of screws  38  (bolts) into the passage holes  25 C and  27 C, and fastening nuts  39  to the screws  38 . 
     Heat Discharging Member  28   
     The heat discharging member  28  is made of a metal material such as aluminum or an aluminum alloy that is molded using aluminum die casting for example, or another material. As shown in  FIG. 14 , the heat discharging member  28  is provided with a mounting portion  29  on which the spacer  40  is mounted, a peripheral wall portion  33  that protrudes upward from the peripheral edge of the mounting portion  29 , and heat discharging fins  37  that are provided on the bottom side of the mounting portion  29 . 
     The mounting portion  29  has a flat upper surface. The mounting portion  29  has, at positions on the edge side of the mounting portion  29 , a plurality of screw holes  31 A for screwing screws, a plurality of positioning holes  31 B for positioning the spacer  40 , and a clearance recess  31 C. An end of a terminal (not shown) that is inserted into a through hole of the circuit board  21  is arranged in the clearance recess  31 C. The mounting portion  29  has recesses  32 A and  32 B at positions that correspond to the coil  27  (not shown) and the stud bolt  56 . 
     In a state in which the spacer  40  and the circuit board  21  are stacked on the mounting portion  29 , the peripheral wall portion  33  is higher than the upper end of the circuit board  21 . The peripheral wall portion  33  is divided at positions that correspond to connector portions  17 B and  54 , and the connector terminals  24 . The boss parts  34  with a screw hole protrude outward from the outer side of the peripheral wall portion  33 . 
     Spacer  40   
     The spacer  40  is a rectangular insulating plate having such a thickness that it is not easily bent, and is mounted on the entire upper surface of the heat discharging member  28 . As shown in  FIGS. 6 and 7 , the spacer  40  is provided with a plate-shaped main portion  40 A in a region with which the circuit board  21  is to overlap (region on the right side of  FIG. 7 ), and an extended portion  49  that is contiguous with the main portion  40 A, and extends to a region with which the circuit board  21  is not to overlap (region on the left side of  FIG. 7 ). 
     The main portion  40 A is provided with a plurality of (fourteen in the present embodiment) through holes  41  that are formed through the main portion  40 A, screw passage holes  42 A and  42 B through which the shaft portions of the screws  48  pass, a terminal passage hole  43 , positioning projections  44 A and  44 B, and engaging projections  45 . 
     Each through hole  41  is circular in the shape of a true circle, and is formed through the spacer  40  so as to be able to accommodate a heat transmission portion  47  that transmits heat of the circuit unit  20 A to the heat discharging member  28 . Two or four through holes  41  are lined up in a plurality of lines arranged at equal intervals (intervals in a left-right direction of  FIG. 7 ), and in each of the lines, the through holes  41  are lined up at equal intervals (intervals in the up-down direction of  FIG. 7 ). The through holes  41  have a tapered shape such that the hole diameter thereof increases toward the lower side. 
     For the heat transmission portions  47 , members are used that have a high heat conductivity, and that may be, for example, a thermosetting or thermoplastic adhesive agent, an adhesive sheet obtained by applying an adhesive agent to a base material, a heat discharging grease, a heat radiation gel, a heat conduction sheet, or the like. When an adhesive agent is used, a mixture of two types of epoxy adhesive agents that solidifies at room temperature may be used, for example. Alternatively, for example, an insulating film made of a synthetic resin to both surfaces of which an insulating adhesive agent is applied may be used. The heat transmission portion  47  is arranged overlapping, on its upper side, with at least a part of the electronic component  26 , and heat of the electronic component  26  transmitted to the heat transmission portion  47  is discharged from the heat discharging member  28 . 
     The screw passage holes  42 A and  42 B are formed at positions close to the peripheral edge of the spacer  40 . The terminal passage hole  43  is formed through the spacer  40  in a rectangular shape. The positioning projections  44 A and  44 B are columnar, and are arranged at positions close to the corners on the peripheral edge of the spacer  40 . The positioning projections  44 A project upward from the upper surface of the spacer  40  in a columnar shape, and the positioning projections  44 B project, as shown in  FIG. 11 , downward from the lower surface of the spacer  40  in a columnar shape. 
     The engaging projections  45  can engage with portions that are contiguous with the connector terminals  24 . As shown in  FIG. 7 , the engaging projections  45  project upward in the vicinity of the rear side of the connector portion  54 , and can be inserted into engaging holes  24 A (see  FIG. 5 ) of the circuit board  21 . Accordingly, the engaging projections  45  receive a force that acts on the connector terminals  24  when the connector portion  54  is engaged with a counterpart connector (not shown), so that the force at the time of the engagement is unlikely to act on the circuit unit  20 A. 
     As shown in  FIG. 6 , the extended portion  49  is provided with a flat extended portion  50  that is plate-shaped and is contiguous with the main portion  40 A in a coplanar manner, and a plurality of accommodating portions  51  to  54  that accommodate a part of the circuit unit  20 A. The accommodating portions  51  to  54  include nut accommodating portions  51  that accommodate nuts  39 , a coil accommodating portion  52  that accommodates the coil  27 , a terminal accommodating portion  53  that accommodates the stud bolt  56  serving as an external connection terminal, and a connector portion  54  that accommodates the connector terminals  24 . 
     The nut accommodating portions  51  are formed as recesses formed in the flat extended portion  50 , and have a shape that corresponds to the rectangular nuts  39  so as to prevent the nuts  39  from rotating. Each nut accommodating portion  51  has, on the bottom surface thereof, a hole  51 A that is formed through the flat extended portion  50 , and whose diameter is reduced stepwise, so that the front end of the screw  38  can be passed therethrough. 
     The coil accommodating portion  52  has a bottom portion  52 A that is recessed further downward than the flat extended portion  50 , and a wall portion  52 B that has the shape of a rectangular tube that encloses the entire periphery of the coil  27 . The bottom portion  52 A is fitted into the recess  32 A of the heat discharging member  28 . The wall portion  52 B has substantially the same height as the coil  27  accommodated in the coil accommodating portion  52 . The wall portion  52 B is divided at positions from which the coil wire  27 B is drawn. 
     As shown in  FIG. 4 , the terminal accommodating portion  53  accommodates a plate-shaped rectangular base portion  56 B of the stud bolt  56 , which includes the base portion  56 B and a columnar pillar portion  56 A, the terminal portion  25 A, and a metal connection plate  55 . Specifically, the terminal accommodating portion  53  has accommodating recesses  53 B into which the base portion  56 B can be inserted from the front side while sliding to a predetermined position, and cut-out portions  53 A into which the pillar portion  56 A can be inserted. The connection plate  55  is rectangular, and has a bolt hole  55 A that is formed through the connection plate  55 , and into which the pillar portion  56 A of the stud bolt  56  can be inserted, and one side in a longitudinal direction of the connection plate  55  is placed on the terminal portion  25 A. 
     A separate auxiliary member  60  is arranged in the vicinity of the coil accommodating portion  52  and the terminal accommodating portion  53 . As shown in  FIGS. 12 and 13 , the auxiliary member  60  includes a lid  61  that covers the coil accommodating portion  52 , and a box body  62  that is arranged around the terminal accommodating portion  53  to form the box portion  16 . 
     As shown in  FIG. 8 , the connector portion  54  is a connector housing that includes a hood portion  54 A that encloses the connector terminals  24 , and a rear wall portion  54 B that closes the hood portion  54 A. The rear wall portion  54 B has terminal insertion holes  54 D that are formed through the rear wall portion  54 B, and into which the connector terminals  24  are inserted. A flange  54 C that extends along the peripheral edge of the main portion  40 A protrudes from the connector portion  54 . 
     As shown in  FIG. 6 , the spacer  40  includes, on the peripheral edge thereof, a thick-walled portion  40 B that has a large thickness on the upper surface side, and a band-shaped protruding piece  46  that is raised upward. The spacer  40  is made of an insulating plastic (synthetic resin), and is formed in one piece as a whole by injecting the synthetic resin into a mold. In other words, the spacer  40  employs a material that has such a strength that it does not easily deform due to a force acting at the time of tightening the screws  48 . 
     The following will describe a method for manufacturing the circuit assembly  20  and the electrical junction box  10 . 
     The spacer  40  is mounted on the mounting portion  29  that is the upper surface of the heat discharging member  28  ( FIG. 16 ). Then, the nuts  39  are accommodated in the nut accommodating portions  51 , and an adhesive agent is applied into the through holes  41  of the spacer  40 . 
     Solder paste is added to the electrically conducting path of the circuit board  21  that is obtained by adhering the printed board  21 A and the busbar board  21 B to each other using an adhesive member, the electronic components  26  are arranged at predetermined positions, and the resulting object is passed through a reflow furnace to be subjected to reflow soldering. Thereby, the circuit unit  20 A in which the electronic components  26  are mounted on the circuit board  21  is achieved. 
     Then, by inserting the connector terminals  24  of the circuit unit  20 A into the terminal insertion holes  54 D of the connector portion  54 , the circuit unit  20 A is mounted on the spacer  40  ( FIG. 17 ). 
     Then, the coil  27  is accommodated in the coil accommodating portion  52 , and the ends of the coil wire  27 B and the terminal portions  25 B of the circuit unit  20 A are fastened to each other with the screws  38  and the nuts  39 . Furthermore, the stud bolt  56  is accommodated in the terminal accommodating portion  53 , and the connection plate  55  is mounted. Furthermore, the screws  48  are inserted into the screw holes  22 , the screw passage holes  42 A and  42 B, and the screw holes  31 A, and are screwed to fix the circuit board  21  and the heat discharging member  28  to each other, thereby achieving the circuit assembly  20  (see  FIG. 3 ). The shield cover  11  is placed onto the circuit assembly  20  and the screws  13  are screwed, thereby achieving the electrical junction box  10  ( FIG. 1 ). 
     According to the present embodiment, the following functions and effects can be attained. 
     According to the present embodiment, since the main portion  40 A of the spacer  40  is disposed between the circuit unit  20 A and the heat discharging member  28 , it is possible to keep the distance between the circuit unit  20 A and the heat discharging member  28  constant without using a jig. Furthermore, since the accommodating portions  51  to  54  of the spacer  40  accommodate a part (the nuts  39 , the coil  27 , the stud bolt  56 , and the connector terminals  24 ) of the circuit unit  20 A, it is possible to hold parts of the circuit unit  20 A at predetermined positions using the structure of the spacer  40 , instead of providing a separate frame-shaped resin member for accommodating parts of the circuit unit  20 A. Accordingly, it is possible to hold parts of the circuit unit  20 A at predetermined positions while keeping the distance between the circuit board  21  and the heat discharging member  28  constant, with a simple configuration. 
     Furthermore, the main portion  40 A and the accommodating portions  51  to  54  are molded in one piece using a resin. 
     With this, it is possible to simplify the configuration compared to a case where, for example, a separate accommodating portion is fixed to the main portion  40 A to form a spacer. 
     Furthermore, the accommodating portions  51  to  54  accommodate the nuts  39  of the circuit unit  20 A. 
     With this, by providing the nut accommodating portions  51  obtained by reducing the thickness of the spacer  40  locally, it is possible to hold the nuts  39  in positions, and thus it is possible to simply the configuration for holding the nuts  39  in positions. 
     Furthermore, the main portion  40 A is provided with through holes  41  that are formed through the main portion  40 A, and heat transmission portions  47  that are arranged in the through holes  41 , and are configured to transmit heat of the circuit unit  20 A to the heat discharging member  28 . 
     With this, the heat transmission portions  47  allow heat of the circuit unit  20 A to be discharged from the heat discharging member  28 . 
     Furthermore, the circuit unit  20 A and the heat discharging member  28  are fastened to each other with screws  48 . 
     With this, the circuit unit  20 A and the heat discharging member  28  can be fixed to each other firmly with the screws  48 , while the spacer  40  receives a force acting when the circuit unit  20 A and the heat discharging member  28  are fastened to each other with the screws. 
     OTHER EMBODIMENTS 
     The present invention is not limited to the embodiment explained in the foregoing description given with reference to the drawings, and the technical scope of the present invention encompasses, for example, the following embodiments. 
     (1) The parts of the circuit unit  20 A that are accommodated by the spacer  40  are not limited to the above-described nuts  39 , coil  27 , stud bolt  56 , and connector terminals  24 , and may be other components of the circuit unit. 
     (2) The material of the heat discharging member  28  is not limited to aluminum or an aluminum alloy, and may be any material as long as it is a metal material that has high heat conductivity. For example, the heat discharging member  28  may be made of copper or a copper alloy. 
     (3) Although the circuit unit  20 A and the heat discharging member  28  are fastened to each other with the screws  48 , the circuit unit  20 A and the heat discharging member  28  may be fixed to each other using a fixation means (for example, a lock mechanism) other than the screws.