1.  Field of Invention
The present invention relates to an electrical junction box for a vehicle, in particular a box to be connected to a wire harness for a vehicle.  The invention is intended to provide a junction box which is thin and compact even though the number of circuits is increased.  The invention also provides a vehicle, such as an automobile, having the electrical junction box mounted on it. 
2.  Description of Related Art
Recently, the rapid increase in the number of electric and electronic component parts which are mounted on a vehicle has led to increase in the number of circuits to be accommodated in a junction box in the vehicle.  When forming branch circuits at high density, it is necessary to mount a large number of component parts on the junction box, which increases the number of assembly stages. 
The assignees of the present application proposed the junction box 1 shown in present FIG.  21 in JP-A-2000-112691 (corresponding to EP-A-1145914 and U.S. patent application Ser.  No.  09/833595).  The junction box of FIG.  21 is intended to be thin, capable of permitting circuit alteration and reducing the time and labor required for its assembly from component parts. 
In the junction box 1 of FIG.  21, a connector connection circuit (base circuit), a fuse connection circuit, and a relay connection circuit provided in the junction box are formed separately as a connector module 2, a fuse module 3 and a relay module 4.  The connector module 2, the fuse module 3 and the relay module 4 are incorporated in the casing composed of the lower case part 5 and the upper case part 6. 
In each of the connector module 2, the fuse module 3 and the relay module 4, bus bars 2b, 3b and 4b are fixed to insulation substrates 2a, 3a and 4a respectively, and project from the periphery of the insulation substrates to which they are attached. 
Because the whole circuit of the junction box is divided into the connector module 2, the fuse module 3 and the relay module 4, overlap of the bus bar tabs can be avoided.  Thus, the formation of multiple layers of bus bars can be prevented.  Therefore, the junction box can be thin, and the circuits of the bus bars can be more easily wired.  Thus, it is possible to reduce the area of the bus bar for module.  Consequently, even though the connector connection bus bars, the fuse connection bus bars and the relay connection bus bars are formed separately, the total area of all the bus bars can be reduced and the area of the junction box can be kept to a minimum. 
Further, when the specification of any one of the connector circuit, the fuse circuit and the relay circuit is altered, it is only necessary to alter the respective module.  Thus, the junction box permits alteration of the specification easily. 
However, the bus bars used as electrical conductors in the modules are generally formed by punching metal sheet into a form corresponding to a complicated configuration of the circuit of the module.  Thus, the yield of the metal sheet is low.  Further, when a circuit alteration is made, it is necessary to make a new punching die, which can increase costs. 
Further, depending on a circuit configuration, it may be impossible to form the circuit as a single layer.  Thus the number of bus bar layers increase. 
For example, as shown diagrammatically in FIG.  22A, in connecting circuits C1 and C2 to connectors 7A and 7B of a connector module 2 and to a fuse 8 of a fuse module 3 disposed on the side of the connector module, the circuits C1 and C2 of the connector module 2 cannot be connected to the fuse 8 unless the circuits C1 and C2 are disposed in separate layers.  Thereby, the number of layers is increased. 
Although the number of component parts mounted on a vehicle has increased rapidly, space for the junction box has remained limited.  Thus, it is essential to make the junction box as thin as possible. 
It is an object of the present invention to provide a junction box which is thin and can be manufactured at a low cost, in particular by improving the yield of a conductive metal plate. 
It is a further object of the invention to simplify the wiring and conductor arrangements in a junction box and provide simplified methods of making the connector module of the junction box. 
According to a first aspect of the invention in, there is provided an electrical junction box having a casing and an electrical circuit in the casing adapted to make electrical connection, in use, to electrical connectors, fuses and relays.  The electrical circuit comprises a fuse connection circuit, a relay connection circuit and a connector connection circuit, which is electrically connected to the fuse connection circuit and the relay connection circuit.  The casing comprises a fuse circuit portion, containing the fuse connection circuit, and a relay circuit portion, containing the relay connection circuit.  The casing also has two laterally opposite sides, each of which forms a connector accommodation portion adapted to receive, in use, at least one electrical connector. 
Additionally, the electrical junction box may further have, mounted within the casing, a connector module providing the connector connection circuit that comprises a plurality of insulation substrates stacked one on another and each having a first main surface and a second main surface opposite the first main surface.  A plurality of parallel elongate bus bars may be arranged on the first main surface of each substrate and extends in a first direction, and a plurality of parallel flexible conductors may be arranged on the second main surface of each insulation substrate and extends in a second direction orthogonal to the first direction.  A plurality of apertures pass through each insulation substrate from the first main surface to the second main surface.  The bus bars and the flexible conductors are connected to each other by welding to provide desired circuit connections at these apertures.  The bus bars of each insulation substrate are oriented in the lateral direction of the casing between the opposite sides, some which extend from the insulation substrates in the first direction and provide tabs that project into the connector accommodation portions. 
The flexible conductors of each connector module may be single-core wires, or conductors of a flexible flat cable arranged on the second main surface of the insulation substrate, the flexible flat cable comprising flexible insulation material in which the conductors are held. 
Thus in the connector module, the elongated bus bars and the flexible conductors cross each other, with the insulation substrate interposed between them, and are connected to each other at crossing positions to form the circuit of the connector module.  Thus, it is possible to set the interval between the bus bars equal to the interval between the terminals of a connector to be attached to the box, in use.  Thus, the tabs formed at both ends of the bus bars can project horizontally into the connector accommodation portion formed on the side surface of the box, with or even without bending the tabs. 
In the circuit shown in FIG.  22B, in comparison with that of FIG.  22A, the conductors 21 can be connected to the fuses 35 while connecting both ends of the bus bars 22, constituting circuits C1 and C2, of the connector module 11 to connectors 7Axe2x80x2 and 7Bxe2x80x2.  Thus, it is possible to connect the bus bars 22 to the conductors 21, disposed on the other side of the insulation substrate 20, orthogonally to the bus bars 22, with the insulation substrate 20 interposed between the bus bars 22 and the conductors 21.  Consequently, this simple circuit of the connector module 11 can be formed from a single circuit layer having the bus bar disposed on one surface of the insulation substrate and the conductors disposed on the other surface thereof.  This simple example illustrates the principle of this aspect of the invention.  That is, it is possible to reduce the number of layers of the bus bar to produce a thin junction box. 
Even though the connector accommodation portion is formed on the side surface of the box, the tabs of the bus bars can project into the connector accommodation portion at the side surface of the side case without interference from adjacent tabs or deformation thereof.  Further, even though the connector is disposed on the side surface of the box, the bus bars can be disposed in a simple construction.  Thus, a relay terminal for connecting bus bars interlaminarly is unnecessary and the construction of the circuit of the connector module can be kept simple. 
The number of layers of the substrates of the connector module may be equal to the number of rows of terminals of a connector which fits in the connector accommodation portion. 
That is, as described above, the tabs formed at both ends of the bus bar disposed on one surface of each substrate of the connector module project into the connector accommodation portions.  Thus, the number of layers of the substrates of the connector module may be equal to the number of rows (stages) of terminals of the connector, which fits in the connector accommodation portion.  In other words, the connector can be easily disposed on the side surface of the box when the number of the rows (stages) of the connector is equal to the number of the substrates. 
A further layer consisting of bus bars may be formed as an additional, e.g. lowermost layer, of the connector module.  The total of the number of layers of the substrates and the number of further layers of the bus bars may be not less than the number of rows (stages) of terminals of the connector which fits in the connector accommodation portion.  Preferably, the elongate bus bars are not connected to the power source side and to the power supply side of the fuses.  For efficient wiring of the bus bars, it is preferable to use one bus bar having a plurality of fuse connection terminals formed at one end thereof.  Thus as the bus bar having a plurality of fuse connection terminals formed at one end thereof, it is preferable not to use the elongate bus bars but use the bus bars formed by punching a conductive metal plate corresponding to the configuration of a desired circuit.  The elongate bus bars may be disposed on a layer on which the bus bar formed by punching the conductive metal plate is disposed, and the ends of the elongate bus bars project horizontally as tabs.  Consequently, the total of the number of the substrates and the number of the further layers of the bus bars is equal to the number of the rows (stages) of terminals of the connector. 
The ends (tabs) of the elongate bus bars that project into the connector accommodation portion may be kept flat, so that the tabs of different bus bar layers do not interfere with each other.  Otherwise, if the tabs are bent and project from the bus bars disposed on one substrate, the tabs may interfere with tabs projected from the substrates of other layers. 
However, bent tabs a bus bar that project into the connector accommodation portion may be may be accommodated if bent in a manner that kept the tab horizontal, e.g. in the shape of a letter xe2x80x9cLxe2x80x9d or a single zig-zag.  By bending the tabs of the same layer in the same configuration and arranging the tabs to remain parallel with one another, and bending the tabs of the bus bars from other layers in the same configuration, interlaminar interference between the tabs is avoided. 
Compared to the conventional process of forming bus bars, such as by punching a conductive metal plate corresponding to the configuration of a circuit, it is possible to improve the yield of the conductive metal plate considerably, by employing strip-shaped elongate bus bars of uniform width.  Further, the construction can cope with alteration of the circuit construction by simply changing the position where the flexible conductors and bus bars cross each other and are welded to each other.  Because it is unnecessary to alter the conductive material itself with the change of the circuit construction, the construction can easily permit alteration of the circuit construction without increasing the manufacturing cost. 
According to a second aspect of the invention in there is provided an electrical junction box having a casing, and an electrical circuit in the casing adapted to make electrical connection, in use, to electrical connectors, fuses and relays.  The electrical circuit comprises a fuse connection circuit, a relay connection circuit and a connector connection circuit which is electrically connected to the fuse connection circuit and the relay connection circuit. 
The casing comprises a fuse circuit portion, containing the fuse connection circuit, and a relay circuit portion, containing the relay connection circuit.  The electrical junction box may further comprise a connector module, mounted in the casing, which provides a connector connection circuit that comprises at least one insulation substrate having a first main surface and an opposite second main surface, and a plurality of spaced parallel flexible conductors arranged on the second main surface.  The relay connection circuit comprises a plurality of bus bars, each having one end arranged to make a connection, at least, in use, to relays and another end that constitutes a pressure connection terminal, which is connected by pressure connection directly to intermediate points of at least some of the flexible conductors of the connector module.  In this construction, the connector module is formed with spaced conductors, e.g. parallel with one another, and the pressure connection terminals at the ends of the bus bars of the relay connection circuit are connected to the intermediate points of the conductors by pressure connection, which reduces the number of welded connections required. 
The ends of the conductors of the connector module may be connected, e.g. by pressure connection, to the terminals formed at an end of the bus bars of the fuse module, and through relay terminals the other ends of the conductors may be connected to an electronic control unit accommodated in the junction box.  Thereby the circuit of the connector module can be connected to the relay module, the fuse module and the electronic control unit by pressure connections between the conductors and the terminals.  By effectively utilizing the one end, the intermediate portion and the other end of the conductors of the connector module, the circuit of the connector module can be connected to the relay module, the fuse module and the electronic control unit by pressure connections instead of welding bus bars to each other.  Thus, it is easy to perform a circuit connection operation.  Further, it is possible to solve the problem of warping of the bus bars, which occurs due to the thermal strain to which the bus bars are subjected when they are welded together. 
The pressure connection terminals at the ends of each of the bus bars, connected to terminals of the relays of the relay module respectively, are preferably arranged in parallel with one another and connected respectively by pressure connection to the conductors, which are parallel in the connector module.  This construction allows the connection between the circuit of the relay module and that of the connector module to be accomplished in a one-time pressure connection operation. 
The relay module may be of a direct mounting type.  That is, the relay may be mounted on a body having a bus bar formed by insert moulding.  A terminal of the relay penetrates through apertures formed in the body and the bus bar, and the terminals of the relay may then be soldered to the bus bar.  This construction allows the height of the relay to be kept to a minimum.  Thereby it is possible to make the junction box thin. 
The preferred layout of the junction box would have the connector module mounted in the lower portion of the casing, the fuse circuit portion located laterally of the connector module at a first side of the casing, the relay circuit portion located above the connector module at the first side of the casing, an electronic control unit mounted in the casing above the connector module, the connector accommodation portion of the casing, to receive at least one electrical connector, in use, located at a further side thereof, extending orthogonally to the first side thereof, and the bus bars of the connector module project into the connector accommodation portion to constitute tabs therein for connection to the connector, in use. 
According to a third aspect of the invention in there is provided an electrical junction box having an electrical circuit adapted to make electrical connection, in use, to electrical connectors, fuses and relays.  The electrical circuit comprises a fuse connection circuit, a relay connection circuit and a connector connection circuit, which is electrically connected to the fuse connection circuit and the relay connection circuit.  At least one of either the fuse connection circuit, the relay connection circuit and the connector connection circuit comprises a circuit module having a plurality of elongate bus bars arranged parallel to each other and extending in a first direction.  A plurality of flexible conductors arranged parallel to each other and crossing the bus bars are arranged in a second direction, orthogonal to the first direction, where the flexible conductors and the bus bars are electrically connected to each other at a plurality of their mutual crossing points to provide the desired circuit connections. 
The layout allows the side surface of the junction box to be effectively utilised.  Thereby it is possible to make the junction box thin. 
Conventionally, a conductive metal plate is punched in a shape corresponding to the configuration of a circuit to form an electric conductor.  But according to this aspect of the present invention, the desired circuit can be formed by crossing the elongate bus bars and the flexible conductors and connecting them to each other at necessary crossing points.  Therefore, there is little loss of the conductive metal plate and it is possible to greatly improve the yield of the conductive metal plate.  In addition, when it is necessary to change the construction of the circuit, it is not necessary to alter the conductors but it is only necessary to change the position where the bus bars and the flexible conductors are connected to each other.  Accordingly, the junction box of the present invention can be manufactured at a low cost and can cope with the alteration of the circuit.  At the crossing points, the bus bars and the conductors, e.g. single-core wires, may be joined to each other in openings formed in the insulation substrate by resistance welding or soldering. 
In the case where a bare wire is used as the flexible conductor, it is unnecessary to remove an insulating coating at the position where the wire and the bus bar are connected to each other.  However, it is possible to use wire having a core wire coated with an insulation coating material.  Alternatively, the flexible flat cable described herein above may be used. 
Optimally, the wires and the bus bars may be connected to each other by resistance welding in the openings formed in the insulation substrate.  However, soldering may be used as described above.  In addition, ultrasonic welding, gas welding or laser welding may also be used. 
The circuit module may have a plurality of circuit substrates layered one upon another with insulation interposed between the circuit plates adjacent to each other, with each of the circuit substrates having flexible conductors disposed on one surface and elongate bus bars disposed on the other surface. 
The invention further provides a method of forming an electrical circuit module comprising the steps of: fixing a plurality of bus bars to a first main surface of each of a plurality of insulation substrates; arranging flexible conductors on a second main surface opposite the first main surface of each insulation substrate, while the insulation substrates are arrayed in a row, with the flexible conductors extending continuously over the insulation substrates in said row; connecting the bus bars to the flexible conductors at mutual crossing points thereof via apertures in the insulation substrates to form desired circuit connections; bending the portions of the flexible conductors that extending between adjacent pairs of the insulation substrates to bring the insulation substrates into a stack one above another; and removing portions of said flexible conductors not wanted in the completed circuit. 
By forming the circuit module in the manner described, the flexible conductors may be wired collectively or continuously and operability of the method can be greatly improved. 
According to another aspect of the invention, there is provided an electrical junction box having an electrical circuit adapted to make electrical connection, in use, to electrical connectors, fuses and relays.  The electrical circuit comprises a fuse connection circuit, a relay connection circuit and a connector connection circuit, which is electrically connected to the fuse connection circuit and the relay connection circuit.  The electrical junction box may comprise a connector module providing the connector connection circuit, which comprises an insulation substrate having a first main surface and a second main surface opposite the first main surface, and a plurality of first electrical conductors on the first main surface and a plurality of second electrical conductors on the second main surface.  The first electrical conductors are parallel to each other and can extend in a first direction and the second electrical conductors are parallel to each other and extend in a second direction, orthogonal to the first direction.  Thus, the second electrical conductors cross the first electrical conductors at crossing points. 
The first and second conductors may be selected from the following: (a) the first electrical conductors are elongate bus bars and the second electrical conductors are flexible conductors of a flexible flat cable comprising flexible insulation material in which the flexible conductors thereof are held, (b) the first electrical conductors are individual flexible single-core wires, and the second electrical conductors are flexible conductors of a flexible flat cable comprising flexible insulation material in which the flexible conductors thereof are held, and (c) both the first and second electrical conductors are flexible conductors of a flexible flat cable comprising flexible insulation material in which the flexible conductors thereof are held.  In addition, at a plurality of the crossing points, the mutually crossing first and second electrical conductors may be connected to each other to provide the desired electrical junctions. 
In this aspect of the present invention, elongated bus bars and flexible flat cables (FFC) are used.  Alternatively, a FFC and a flexible single-core wire (e.g. bare wires) or two FFCs may also be used in place of the bus bars.  The conductors on the one surface of the insulation substrate and the conductors on the other surface thereof are crossed and connected to each other, preferably by welding, at necessary cross points to form the desired circuit.  Therefore, there is little loss of the conductive metal plate, whcih greatly improves the yield of the conductive metal plate.  In addition, when it is the construction of the circuit is changed, it is not necessary to alter the electric conductors, instead, only the positions at which the electric conductors are connected to each other need to be changed.  Accordingly, the junction box of the present invention can be manufactured at a lower cost and provides easier alteration of the circuit. 
In cases where a FFC and single-wire core (bare wire) are used in combination, or where only flexible flat cables are used in stead of a bus bar it is unnecessary to remove the insulating coating material at a connection position.  The FFC contains the electric conductors arranged in parallel with one another in the insulation film.  Thus, it is possible to dispose only one FFC containing a desired number of electric conductors laminated with the insulation film on the insulation substrate and thereby reduce the time and labor required for assembly. 
The electric conductors may optimally be connected on the one surface of the insulation substrate and to those on the other surface thereof to each other by resistance welding.  However, soldering, ultrasonic welding, laser welding or gas welding may also be used. 
The connector module may include a plurality of circuit layers comprising insulation substrates and conductors, stacked one upon another with insulation plates interposed between the adjacent layers.  The FFC has the electric conductors laminated with the insulation film.  Thus when the bus bar, the single-core wire or the FFC is located at the interface between two layers, they are insulated.  In this case, the use of the insulation plate can be omitted. 
In this specification the term xe2x80x9cpressure connectionxe2x80x9d refers to the connection of two conductors that is achieved by press-fitting a gripping part onto a gripped part, the fitting force being maintained to keep a permanent connection.  In the embodiments, for example, a wire is inserted into a groove on the tab of a bus bar, which maintains a gripping pressure on the wire. 
The flexible conductors used in the invention should be selected to be suitably flexible without damage, e.g. to allow the connections through the insulating substrates.  Their flexibility is in contrast to the relative rigidity of the bus bars, which generally retain their shape, though being capable of being deformed into a desired shape.