Electric junction box

An electric junction box for installation in an automobile includes a power distributor as an internal circuit component of the electric junction box. The power distributor has relays mounted on one side of printed circuit board and connected to the printed conductor, and has bus bars fixed on the other side of printed circuit board. The power distributor is divided into a power distributor for a battery side connection and power distributor for an alternator side connection. The power distributor for the battery side connection and the power distributor for the alternator side connection are placed facing each other oppositely, and have respective heat sinks facing outwardly. A branch circuit block is provided in the lower region of power distributors, which is formed from a lamination of bus bars and insulation plates.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electric junction box. Specifically, the electric junction box is configured for installation in an automobile and includes a power distributor (PD). The PD includes relays, as well as other electronic components, mounted on one side of a circuit board and bus bars fixed on the other side of the circuit board.

2. Description of Related Art

Conventionally, an electric junction box, such as those junction boxes for distributing electric power to each of the wire harnesses in an automobile, has a large number of relays and fuses, and a connector-connecting portion is formed on the outer surface of the box for connecting bus bar circuits to wire harnesses, the bus bar circuits being contained inside the electric junction box. In recent years, the number of electrical circuits in an automobile has increased in accordance with the sharp increase in the number of electronic components installed in an automobile, as the automobile becomes more and more sophisticated. Therefore, the number of relays mounted in an electric junction box for installation in an automobile has become larger, thereby forcing the electric junction box to become more dense, as well as larger.

In response to such situation, an electric junction box has been provided with a power distributor (PD) built therein. The PD includes semiconductor switching devices (FET) and mounting relays such as SMD relays mounted on a printed circuit board, and a heat sink fixed on the other side of the printed circuit board.

For example, in Japanese Laid Open Patent Publication No. 2001-319708, shown inFIG. 5of the present application, electric junction box1is disclosed, which includes power distributor PD2and branch circuit block5. In PD2, semiconductor switching device (FET)3is mounted on a printed circuit board; a bus bar is fixed on the back-side of the printed circuit board; FET3, which requires large electrical current, is connected to the bus bar; and heat sink4is attached to the bus bar. Branch circuit block5is made from the lamination of bus bars and insulation plates. On the lower surface of case6of electric junction box1, connector housings7are provided for permitting insertion of connectors of wire harnesses (not shown) installed in a vehicle. On the upper surface of case6, fuse housing8is provided. Connector housings7and fuse housing portion8are connected to branch circuit block5.

However, as it stands now, PD2of electric junction box1is made by using single circuit board. Since PD2is laterally juxtaposed to branch circuit block5in a horizontal direction, electric junction box1is enlarged by an amount measured by the dimensions of PD2. This causes a problem in that the installation space required for installing electric junction box1in a vehicle becomes large. Further, when PD2is laminated on the lower surface of branch circuit block5for the purpose of minimizing the horizontal area of electric junction box1, it puts restrictions on locations for connector housings7. Power input and output between a wire harness and PD2is done via branch circuit block5from connector housings7. Therefore, when making a design for the arrangement of connectors for each destination, there is a problem that circuit wirings of PD2and branch circuit block5become complicated.

Further, since heat sink4is exposed only on the lower surface of case6for radiating outwardly the heat generated in PD2, it is possible that, depending on the position of electric junction box1relative to other components in a vehicle, the heat radiation capability of electric junction box1is not sufficient.

The present invention is provided to address the above-described problems. That is, the present invention reduces the size, simplifies, and enhances the heat radiation capability of an electric junction box having PDs built in it.

SUMMARY OF THE INVENTION

An objective of the present invention is to reduce the size and simplify an electric junction box having a power distributor (PD) mounted therein, as well as to provide a configuration for the electric junction box that enhances its heat-radiation capability.

Accordingly, one feature of the present invention is to provide an electric junction box for installation in an automobile. The electric junction box includes a power distributor that is an internal circuit component of the electric junction box. The power distributor has relays and other electronic components mounted on one side of a printed circuit board and connected to a printed conductor, has bus bars fixed on the other side of said printed circuit board, and has heat sinks attached to the bus bar side of the printed circuit board.

The power distributor includes a power distributor for a battery side connection and a power distributor for an alternator side connection. The power distributor for the battery side connection and the power distributor for the alternator side connection face each other and each have the heat sinks facing away outwardly from the electric junction box. A branch circuit block is arranged perpendicular to the power distributor for the battery side connection and the power distributor for the alternator side connection, and is constructed from a lamination of bus bars and insulation plates.

Ends of the bus bars of the power distributors may be welded to the ends of the bus bars of the branch circuit block. The power distributor for the battery side connection and the power distributor for the alternator side connection may be vertically disposed. The branch circuit block may be horizontally disposed in a lower region of the power distributor for the battery side connection and the power distributor for the alternator side connection. The branch circuit block may have a bus bar connected to a connector at an end of a wire harness, in which the connector at the end of the wire harness is inserted into a connector housing provided on a lower case of the electric junction box.

Further, the electric junction box may include power input bus bars having a bus bar for a battery connection and a bus bar for an alternator connection. The power input bus bars may be disposed in an upper region of the power distributor for the battery side connection and the power distributor for the alternator side connection, and is connected via fuses to the bus bars of the power distributor for the battery side connection and the power distributor for the alternator side connection.

The bus bar for the battery connection and the bus bar for the alternator connection may have branched insulation displacement connection tabs, and are connected to fuses by insulation displacement connections by inserting input terminals of the fuses into slots of the insulation displacement connection tabs of the bus bar for the battery connection and the bus bar for the alternator connection.

The bus bars of the power distributor for the battery side connection and the power distributor for the alternator side connection have insulation displacement connection tabs, and are connected to the fuses by insulation displacement connections by inserting the output terminals of the fuses into the slots of the insulation displacement connection tabs of the power distributor for the battery side connection and the power distributor for the alternator side connection.

Another feature of the present invention is to provide an electric junction box. The electric junction box includes a power distributor which includes a first power distributor for a battery side connection and a second power distributor for an alternator side connection. The first and second power distributors generally face each other, and each have a printed circuit board on an interior side, a heat sink on an exterior side, and a bus bar between the printed circuit board and the heat sink. The branch circuit block includes insulation plates and bus bars.

The branch circuit block may be arranged substantially perpendicular to the first and second power distributors. The bus bars of the first and second power distributors may be electrically connected to the bus bars of the branch circuit block. Further, the first and second power distributors may be vertically disposed and the branch circuit block may be horizontally disposed adjacent a lower region of each of the first and second power distributors.

The branch circuit block may include a bus bar connected to a wire harness connector, in which the connector is inserted into a connector housing provided on a case of the electric junction box. The electric junction box may further include power input bus bars that include a bus bar for a battery connection and a bus bar for an alternator connection. In this regard, the power input bus bars may be disposed adjacent an upper region of each of the first and second power distributors.

Further, the power input bus bars may be connected via fuses to the bus bars of the first and second power distributors. The bus bar for the battery connection and the bus bar for the alternator connection include branched insulation displacement connection tabs having slots that receive input terminals of the fuses to facilitate an insulation displacement connection. Still further, the bus bars of the first and second power distributors have insulation displacement connection tabs having slots that receive output terminals of the fuses to facilitate an insulation displacement connection.

In the configuration described above, a power distributor in an electric junction box is not formed as a single-piece configuration, but is divided into two parts, i.e., a power distributor for the battery side connection and a power distributor for the alternator side connection, with the two parts facing each other. Therefore, it is possible to avoid an increase in the size of the electric junction box and to reduce the installation space of the electric junction box when it is installed in a vehicle. Further, since the heat sinks of the power distributor (of which the two parts are placed facing each other oppositely) face outwardly, it is possible to radiate heat effectively to the outside of the electric junction box. Additionally, by dividing the power distributor into two parts, the size of each part after the division is smaller. Also, there is the added merit of being easy to be manufacture.

Further, since one or more branch circuit blocks are placed on at least one side of the power distributor (which has its two parts placed facing each other oppositely), the branch circuit block can be utilized for making electrical connections and splices between the two parts of the divided power distributor, thereby simplifying circuit wirings on each side of the power distributor. Consequently, when power distributor circuits can be substantially simplified, it is possible to produce an electric junction box cheaply by having circuit wirings using only bus bars and eliminating printed conductors.

Further, in case where there are design changes in only one of the battery side circuit and the alternator side circuit, it is sufficient to design only for that one side of the power distributor, thereby making it possible to reduce the design load.

Since the circuit connection between the power distributor for the battery side connection, the power distributor for the alternator side connection, and the branch circuit block are implemented by welding together respectively their ends, the reliability of the electrical connection is better than a connector connection and insulation displacement connection.

Also, since the branch circuit block is placed below the vertically placed power distributor, there is no power distributor positioned below the branch circuit block. This provides more freedom in choosing a location for the connector housing on the outer surface of the lower case, and therefore simplifies the circuit wiring of the branch circuit block when making a design for the arrangement of connectors for each destination.

In the configuration described above, over-current circuit breaking functionality is provided by the fuses. The connection can be easily done between the bus bar for the battery connection and the power distributor, and the bus bar for the alternator connection and the power distributor, the bus bars providing electric power input to the electric junction box.

DETAILED DESCRIPTION OF THE INVENTION

The following describes preferred embodiments of the present invention with reference to the drawings.FIG. 2shows electric junction box10of the present embodiment which has two power distributors (hereafter referred to as PDs)14and15placed vertically and facing each other oppositely between upper case11and lower case12. In the lower region of PDs14and15, branch circuit block13is placed horizontally, and is made from the lamination of a plurality of insulation plates24and a plurality of bus bars25.

Fuse housings11aand11bare provided on the topside of upper case11. Heat sink retention groove11c, having a generally U-shaped cross-section, is formed on the sidewall of upper case11. As shown inFIGS. 2 and 3, connector housing12aand battery terminal housing12bare formed on the bottom side of lower case12. Tab25bof bus bar25of branch circuit block13projects into the terminal slot of connector housing12aof lower case12, and is connected with the terminal of the connector that is connected to the end of a wire harness (not shown in the figure).

PD14is the PD for the battery side connection. On one side (the inner side inFIG. 2) of printed circuit board16, relay17is mounted, and part of the terminal of the relay is connected to the printed conductor. On the other side of printed circuit board16, bus bar18is fixed, and having been stamped out with a predetermined circuit pattern. Part of the terminal of relay17penetrates the insulation plate of printed circuit board16and is soldered to bus bar18to make an electrical connection therewith. On the outer side of bus bar18, through an insulation sheet (not shown in the figure), metallic heat sink19is attached. The upper end of bus bar18projects into the upper region above printed circuit board16and forms insulation displacement connection tab18bhaving a slot. The lower end of bus bar18projects into the lower region below the lower edge of printed circuit board16and forms edge portion18a. Heat sink19can also be fin-shaped, for example, to enlarge its surface area.

On the other hand, PD15is the PD for the alternator side connection. On one side (the inner side inFIG. 2) of printed circuit board20, relay21is mounted, and part of the terminal of the relay is connected to the printed conductor. On the other side of printed circuit board20, bus bar22is fixed, and having been stamped out with a predetermined circuit pattern. Part of the terminal of relay21penetrates the insulation plate of printed circuit board20and is soldered to bus bar22to make an electrical connection therewith. On the outer side of bus bar22, through an insulation sheet (not shown in the figure), metallic heat sink23is attached. The upper end of bus bar22projects to the upper region above printed circuit board20and forms insulation displacement connection tab22bhaving a slot. The lower end of bus bar22protrudes into the lower region below the lower edge of printed circuit board20and forms edge portion22a. Heat sink23can also be fin-shaped, for example, to enlarge its surface area.

Insulation displacement connection tab18bof bus bar18of PD14for the battery side connection and insulation displacement connection tab22bof bus bar22of PD15for the alternator side connection are respectively inserted into the output terminal holes of fuse housings11aand11b.

Edge25aof bus bar25of branch circuit block13projects beyond the edge of insulation plate24and bends downwardly. Edges25aare respectively superimposed with and welded to edge portions18aand22a, the welding areas being confined inside lower case12.

Tab25b, which bends and projects downward from bus bar25of branch circuit block13, projects into connector housing12aof lower case12.

Electric power input bus bars28include bus bar26for battery connection and bus bar27for alternator connection and are placed in the upper region of PD14for the battery side connection and PD15for the alternator side connection, with PD14and PD15being placed facing each other oppositely.

Electric power input bus bars28are explained by using bus bar26for a battery connection, as a representative example. As shown inFIG. 4, bus bar26includes vertical portion26a, extending portion26bthat bends from the upper portion of vertical portion26atoward a perpendicular direction, and insulation displacement connection tabs26dthat project from the upper edge of extending portion26bwith intervals. Each of insulation displacement connection tabs26dhave a slot. Lower end portion26cof vertical portion26aprojects into battery terminal receptacle12bof lower case12. Insulation displacement connection tabs26dare inserted into the power input terminal holes of fuse housings11aand11b.

In other words, by plugging fuse F into fuse housing11aor11b, input terminal Fa of fuse F is inserted into the slot of insulation displacement connection tab26dof bus bar26for the battery side connection, thereby connecting fuse F with bus bar26by an insulation displacement connection. In addition, output terminal Fb of fuse F is inserted into the slot of insulation displacement connection tab18bof bus bar18of PD14for the battery side connection, thereby connecting fuse F with PD14by an insulation displacement connection. As a result, bus bar26for the battery side connection is electrically connected through fuse F to PD14for the battery side connection.

Similar to the above-described case for bus bar26for the battery side connection, bus bar27for the alternator side connection is electrically connected to PD15for the alternator side connection through a fuse plugged into fuse housing11b. In this regard, vertical portion27aand extending portion27bmay be seen inFIG. 1.

As shown inFIG. 2, heat sink19of PD14for the battery side connection and heat sink23of PD15for the alternator side connection are exposed to the openings on the lateral sides of electric junction box10. Upper edges19a,23aof heat sinks19and23are kept by heat sink retention groove11cof upper case11. As shown inFIG. 3, heat sink19of PD14for the battery side connection has extending portion19band projecting portion19c. Extending portion19bbends and extends to the side where PD15for the alternator side connection is located. Projecting portion19cis a continuation portion of extending portion19band is pulled out of the case. Heat sink23of PD15for the alternator side connection has projecting portion23b, which is extends from the case. Projecting portion19cand projecting portion23bare bonded together and fastened on vehicle body panel P by bolt B. When it is not required to radiate heat to vehicle body panel P, the configuration of fastening heat sinks to vehicle body panel P by bolt B is not necessary.

In the electric junction box10having the configuration described above, the PD is not formed as a large single-piece configuration, but is divided into PD14for the battery side connection and PD15for the alternator side connection. Additionally, PD14and PD15are placed facing each other oppositely, thereby avoiding an increase in the size of electric junction box10. Further, since heat sinks19and23of PD14and PD15(which are placed facing each other oppositely) are exposed outwardly, it is possible to radiate heat effectively to the outside of electric junction box10. Furthermore, since heat sinks19and23project to the outside of the case and are fastened to vehicle body panel P, heat generated at relays17and21is let out through heat conduction to vehicle body panel P, thereby further enhancing the heat radiation capability.

Since branch circuit block13is positioned in the lower region of PD14and PD15(which are placed facing each other oppositely), the branch circuit block13can be utilized for making electrical connections and splices between PD14and PD15, thereby simplifying the circuit on each PD side. Furthermore, when there is a change in the circuit of one PD, for example, the circuit on the battery side (or the circuit on the alternator side), it is sufficient to design only PD14for the battery side connection (or PD15for the alternator side connection), thereby reducing the design load. PDs14and15without design changes can be used among different types of vehicles or different grades.

In the present embodiment, branch circuit block13is placed horizontally in the lower region of a pair of PDs14and15which are placed vertically. However, branch circuit block13can also be placed horizontally in the upper region of PDs14and15, or in both the lower and the upper regions.

The present disclosure relates to subject matter contained in priority Japanese Application No. 2004-240365, filed on Aug. 20, 2004, which is herein expressly incorporated by reference in its entirety.