A wire harness

Abstract: The wire harness comprises: a main circuit part 1 including an insulated conductor wiring circuit plate 3 in which conductors 8 are arranged on a base insulation film 9 to form a wiring circuit by turning, bowing, crossing, or branching the conductors and covered with a flexible insulation film 12; and a branched connection part 2 including a printed circuit plate 4 connected to a connecting area 14A in the main circuit part 1 through a connecting area 14B formed thereon and adapted to receive leading electrical wires 5. The conductor wiring circuit plate 30 is a flexible circuit plate which has an insulation base film 33, conductors 31 juxtaposed on the base film, an upper coverlet film 32, and a connecting area 36 for the conductors 31 having an adhesive layer 37 on the back side of the film 32. The connecting area 36 is formed by removing a predetermined width 38 of the base film 33 along the lateral direction of the coverlet film 32.

Description: This invention relates to a wire harness to be used in electrical wiring for an electrical device or an office automation device such as a copier (PPC), a personal computer (PC), a facsimile device, a video tape recorder, a video camera, and the like, or in electrical wiring in an instrument panel for a motor vehicle. It is well known that a wire harness for electrical devices, office automation devices, or the like uses an insulated conductor wiring circuit plate or a flexible plain conductor cable (hereinafter referred to as "FPC") in which a conductor circuit is printed on a base film made of a resin film. A wire harness using the FPC has advantages of facilitating the formation of a circuit in accordance with the arrangement of connectors to be coupled, as well as of closing up and compacting the circuit. However, since the FPC to be used in the wire harness requires an etching process, when the FPC is formed into multiple layers to make a complicated conductor circuit, it is necessary to carry out a complicated process, such as double etching, on the front and back sides. This results in high cost. Further, since there are few standard common parts among different circuits on account of the construction of the FPC, the FPC is inferior to the application of circuit alternations and the whole of the wire harness must be produced individually. This also results in high costs. In such a wire harness, the work to connect the FPC to a printed base plate is very troublesome. For convenience of explanation, the conventional work to connect a conventional FPC to the printed base plate will be described below by referring to FIGURES 17 to 20. FIGURES 17 and 19 are perspective views illustrating the FPC connected to the printed base plate. FIGURES 18 and 20 are cross-sectional views of the respective portions. The FPC, as shown in FIGURES 17 and 18, is a flexible plate which has a base film 33, strip-like conductors 31 juxtaposed on the film 33, and a coverlet film 32 attached to the conductors 31. Ends or midportions of the conductors 31 are soldered to conductive paths 35 of the printed base plate or the like to be connected. However, the work for connecting the conductors 31 to a conductive path 35 on the printed base plate 34 is troublesome and takes time, since heat in the soldering copper is transmitted to the coverlet film 32, or excess solder on the connector area causes an electrical short circuit. In order to overcome these shortcomings, Japanese Patent Public Disclosure No. 3-269912 (1991) discloses an FPC, as shown in FIGURE 19, which has a connection area 36 exposing the conductors 31 by removing the coverlet film 32 and the base film 33. Although the FPC disclosed in the above Japanese Patent Public Disclosure No. 3-269912 is easier to connect to the printed base plate 34 in comparison with the conventional FPC having coverlet film 32 on the connection area, the former FPC has the following disadvantages. As shown in FIGURE 20, the connection area 36 having no coverlet film 32 or base film 33 is mounted on the printed base plate 34 which is to be connected, a clearance 42 corresponding to the thickness of the base film 33 is defined between both conductors 31 and the conductive path 35. Consequently, soldering the conductors 31 and the conductive path 35 is difficult, consumes a lot of solders and deteriorates the conductivity between the conductors, since the conductors 31 are electrically connected to each other through the solders filled in the clearance. Further, it is necessary to reinforce the connection area 36 by taping, or to somehow prevent displacement between the conductors during soldering, in order to ensure conductivity on use, since the connection area 36 deteriorates in a mechanical resistance of tension. Accordingly, the above FPC is not suitable for a modern mass production system on account of the connecting work. A main object of the present invention is to provide a wire harness for electrical devices, which can improve the formation of a circuit and reduce its cost. In order to achieve the above objects, we provide, in accordance with the present invention, a wire harness for electrical devices comprising: a main member having a main circuit including an insulated conductor wiring circuit plate in the form of a flexible circuit plate in which conductors are arranged on an insulation base film and an upper coverlet film having a back surface with an adhesive layer thereon is disposed on the conductors, and a branch member including a printed wiring plate having a plurality of conductive paths thereon and mounting holes for receiving connector pins of a connector for leading electrical wires, wherein a connecting area is formed by a predetermined width along an edge of said flexible circuit plate being devoid of only one of said insulation base film or said upper coverlet film thereby leaving a belt-shaped space across the edge of the flexible circuit plate, and said conductive paths of said printed wiring plate have a side exposed in a connection area and are directly and electrically contacted in an overlapping relationship in contact with a corresponding one of the conductors on the insulated conductor wiring plate in the connecting area whereby the adhesive layer on the back surface of the upper coverlet film at positions between the conductors in the belt-shaped space adheres on the printed wiring plate thereby to hold a connection between the flexible circuit plate and the printed wiring plate. In particular, the insulated conductor wiring circuit plate forms the desired main circuit part by using a base insulation film such as polyethylene-terephtalate (PET), polyvinyl chloride (PVC), polyimide (PI), polyphenylene sulfurid (PPS), or the like with a thickness of 10-500 µm; by using a conductor wire such as a soft copper wire, a tin-plated soft copper wire, other plated wires, a copper alloy wire, a clad wire formed by combining different matals or a stripped or sheated cable formed by twisting, a plurality of the same or different wires (for example a magnet cable) with a diameter of 0.03 - 1.0 mm; and by arranging them on the base, insulating film in bent, turned, branched, or crossed patterns. If stripped conductors are used, in order to insulate the exposed portion of the conductor on the insulation film, it is preferably to coat the conductor with an insulation resin, to cover it with the same film as the insulation film, or to laminate the insulation film with an adhesive resin. Thus, the upper exposed portion of the conductor is covered with the insulation material. The printed wiring plate to be connected to the insulated conductor wiring circuit plate may be a known printed circuit plate on a hard or half hard base plate, or a known flexible printed wiring plate. The conductors of the connection areas formed on the paths are connected to the conducting paths on the printed wiring plate by mechanically connecting means, soldering or welding. The leading electrical wires made of flat parallel wires having a connector (a ribbon cord) or a usual wire are connected to the printed wiring plate by soldering a connector pin or welding. The main circuit part including the insulated conductor wiring circuit plate with the desired main circuit of the wire harness is connected to the leading electrical wires to be connected to the electrical devices through the branched connection part of the printed wiring plate. This constructs a wire harness having a desired circuit. Since the wire harness of the present invention has a connecting construction which combines the main circuit part including the insulated conductor wiring circuit plate, and the branched connection part of the printed wiring plate including the leading wires, it is possible to simplify the circuit formation, and to compact the wire harness. Further, since it is possible to change the circuit of the wire harness by changing only the main circuit part, alternation of the circuit of the wire harness can be effected rapidly and conveniently and the branched connection part can be standardized. In addition, the insulated conductor wiring circuit plate can be formed into a multiple layer construction without etching on a crossing array of the conductors. This improves the flexibility of formation of a high density circuit. In order to achieve the above objects, in the flexible circuit plate (FCP) to be used in the wire harness of the present invention, the insulated conductor wiring circuit plate is a flexible circuit plate which has an insulation base film, conductors juxtaposed on said base film, an upper coverlet film, and a connecting area for said conductors. The coverlet film has an adhesive layer on the back thereof. The connecting area is formed by removing a predetermined width of the base film along the lateral direction of the coverlet film. As an alternative to the above FCP, the insulated conductor wiring circuit plate has a connecting area with exposed conductors without using the coverlet film. Since in the FCP the adhesive layer is disposed on the back side of the coverlet film and the connection area for the FCP has no film, exposing the back side of the conductor, there is no harmful clearance between the conductors to be connected and thus the pair of conductors are tightly contacted with each other, by imposing the connection area on the printed base plate in the FCP. The exposed adhesive layer on the back side of the coverlet film between the juxtaposed conductors is attached to the upper surface of the printed base plate or the like so that the connecting posture of the FCP on the printed base plate is fixed. Accordingly, it is possible to interconnect the conductors instantly simply by putting the FCP on the printed base plate, relatively positioning them and pushing them by the touch of a finger. If the FCP has exposed conductors, it is possible to position the FCP by utilizing the exposed conductors or to reinforce the connection by soldering. FIGURE 1 is a perspective view of a wire harness which does not fall within the scope of the invention but is provided to assist in explaining the invention; FIGURE 2 is a partial plan view of an insulated conductor wiring circuit plate in the wire harness shown in FIGURE 1; FIGURE 3 is a partial cross-sectional view of the plate shown in FIGURE 1. FIGURE 4 is a side view of the connection between the plate and leading electrical wires shown in FIGURE 1; FIGURES 5A and 5B are plan views of other versions of the plate shown in FIGURE 1; FIGURES 6A to 6D are plan views of various wiring forms of conductors in the plate shown in FIGURE 1; FIGURE 7 is a perspective view of an alternative wire harness which again does not fall within the scope of the present invention; FIGURE 8 is a partial cross-sectional view of an insulated conductor wiring circuit plate shown in FIGURE 7; FIGURE 9 is a side view of a means for coupling a printed wiring plate to the plate in the wire harness shown in FIGURE 7; FIGURE 10 is a perspective view of an FCP to be used in a wire harness in accordance with the present invention; FIGURE 11 is a perspective view illustrating the connection between a connecting area of the FCP shown in FIGURE 10 and a printed base plate; FIGURE 12 is a cross-sectional view taken along lines XII - XII in FIGURE 11; FIGURE 13 is a cross-sectional view taken along lines XIII - XIII in FIGURE 11; FIGURE 14 is a perspective view illustrating the connection between a connecting area of an FCP of a second embodiment to be used in the wire harness of the present invention and a printed base plate; FIGURE 15 is a cross-sectional view taken along lines XV - XV in FIGURE 14; FIGURE 16 is a cross-sectional view taken along lines XVI - XVI in FIGURE 14; FIGURE 17 is a perspective view illustrating the connection between a conventional FPC and a printed base plate; FIGURE 18 is a cross-sectional view taken along lines XVIII - XVIII in FIGURE 17; FIGURE 19 is a perspective view illustrating the connection between another conventional FPC and a printed base plate; and FIGURE 20 is a cross-sectional view taken along lines XX - XX in FIGURE 17. Referring now to FIGURES 1 to 16, several wiring harnesses including a wire harness in accordance with the present invention will be explained below. FIGURE 1 shows a wire harness which does not fall within the scope of the claims. The wire harness comprises a main circuit part 1 including an insulated conductor wiring circuit plate 3 on an insulation film (hereinafter referred to as "flexible circuit plate" or "FCP") and a branched connection part 2 including a printed circuit plate 4 connected to the main circuit part 1 and adapted to receive leading electrical wires 5. A main circuit 7 formed on the main circuit part 1 is connected through the branched connection part 2 to the leading electrical wires 5 which are connected to the electrical devices. In particular, the FCP 3, as shown in FIGURE 2, has a main circuit 7 which is formed by arranging conductors 8 made of tin-plated soft copper wires with a diameter of 0.1 mm in bent, turned, or branched patterns on an insulation film 9 made of a polyethylene-terephtalate (hereinafter referred to as "PET") with a thickness of 25 µm and having an adhesive layer 10 with a thickness of 40 µm. An insulation film 12 made of a PET film with a thickness of 25 µm and having a thermoplastic adhesive layer 11 with a thickness of 40 µm is coated over the insulated conductor circuit plate 3 so that the conductors are insulated at the upper exposed portion. The piled insulation films 9, 12 are cut along the profile of the circuit formed by the conductors 8 so that the ends of the conductors 8 on one side of the insulation film 9 are closely juxtaposed and exposed to form a connection area 14A. The conductors are spaced with precise pitches of 0.5, 0.3, 1.0, 1.2 mm, etc. As shown in FIGURES 5A and 5B, the conductors are turned or bent on the FCP 3 in compliance with the patterns of the main circuit 7 to be formed, while the insulation film 9 is branched in accordance with the patterns. As shown in FIGURES 6A to 6D, the conductors 8 are wired on the FCP 3 to form branched portions 13, such as parallel connections (6A, 6C, 6D) or a crossing connection (6B), by soldering or welding the intermediate portions of the conductors 8. As shown in FIGURE 1, the printed wiring plate 4 in the branched connection part 2 is a square hard base plate 15 which has a printed conductive path (not shown) on the back side. A connection area 14B is formed along an end of the printed wiring plate 4 by arranging ends 16 of the conductive paths in a very small pitch. The conductors 8 are electrically connected to the ends 16 of the conductive paths by overlapping connection area 14B on connection area 14A on the FCP 3. This overlapping of areas 14A and 14B is fixed by attaching a reinforcing plate 17 to the back side of the FCP 3 and applying the printed wiring plate 4 to the front side of the FCP 3 to form a sandwich construction and securing it by bolts 18. The branched connection part 2 is provided with mounting holes 19 for connector pins at given positions. As shown in FIGURE 4, connector pins 21 of a connector 20 for the leading wires 5 are inserted into the holes 19 and the top ends of the connector pins 21 projecting from the back side of part 2 are soldered to conductive paths 22. The leading wires 5 may be a flat plate-like cable in which a plurality of fine wires are juxtaposed in a very small pitch and connected to connectors 20 at the opposite ends. An alternative arrangement will be explained below. As shown in FIGURE 7, the main circuit part 1, branched connection part 2, and leading wires 5, which constitute the main portion of the wire harness, are not limited to the above-described example of a harness. For example, a single branched connection part 2 may be connected to a plurality of main circuit part 1, a main circuit part 1 which connects a branched connection part 2 to a connection area 14A may be provided with another connection area 14C and connected to another branched connection area 2A or other leading wires, or a main circuit part 1 may be connected to the center position of a branched connection part 2 (not shown). Another arrangement of the FCP or flexible circuit plate 3 is explained by referring now to FIGURE 8. As shown in FIGURE 8, conductors 8 made of a polyurethane-insulated magnet wire are disposed on insulation film 9 made of polyimide (PI) having an adhesive layer 10, and insulation film 12 made of polyimide (PI) having an adhesive layer 11 is coated over the conductors 8 and the film 9. Since the conductors 8 are insulated, it is possible to cross the conductors 8 on the same insulation film 9. Accordingly, it is possible to increase the flexibility in the circuit design of the main circuit part 1 by utilizing the crossing of the insulated conductors. On the other hand, means for interconnecting the main circuit part 1 and the branched connection part 2, as shown in FIGURE 9, are soldering the connector pins 21 of the connector 20 secured to the upper surface of the printed wiring plate 4 to the conductive paths 22 on the back side of the plate 4 and inserting the connection area 14A of the main circuit part 1 into the connector 20; or piling the connection area 14A of the main circuit part 1 on the connection area 14B of the branched connection part 2 and soldering them. Referring now to FIGURES 10 to 16, an embodiment of a work for connecting the FCP to a printed base plate in a wire harness in acordance with the invention will be explained below. First, by referring to FIGURE 10 which illustrates a first embodiment of this invention, an FCP or a flexible circuit plate 30 is formed by juxtaposing strip conductors 31 on a base film 33. A flexible plate is formed by putting a coverlet film 32 on the juxtaposed conductors 31 on the base film 33. The FCP 30 has a connection area 36 which connects the conductors 31 to a conductive path 35 of a printed base plate 34. An adhesive layer 37 is provided between the conductors 31 and the coverlet film 32 so that the adhesive layer 37 spreads over the entire back side of the coverlet film 32. The connection area 36 is provided with an area 38 on which the base film 33 is removed. The non base film area 38 defines a belt-like space across the FCP 30. The back side of the conductors 31 is exposed on the back side of the connection area 36. The adhesive layer 37 on the back side of the coverlet film 32 is exposed between the conductors 31. The conductors 31 are electrically contacted with the conductive paths 35 as shown in FIGURE 11, by piling the connection area 36 on the printed base plate 34 and pushing them so that a front edge 33A of the base film 33 abuts on a rear edge of the printed base plate 34. As shown in FIGURE 13, the adhesive layer 37 on the coverlet film 32 between the conductors 31 adheres on the printed base plate 34 to fix the posture of the FCP on the printed base plate 34. In this embodiment, the adhesive layer 37 is made of an adhesion which acts at room temperature. The top end 39 of the conductors 31 projects from the coverlet film 32 in the connection area 36 in this embodiment so that the FCP 30 can be readily positioned on the printed base plate 34 and the conductors 31 are positively connected and soldered on the conductive paths. FIGURE 14 shows a second embodiment of this invention. The FCP of the second embodiment has the same adhesive layer 37 as that of the first embodiment shown in FIGURE 1. The connection area 36 to be connected to the printed base plate 34 is provided with the same non base film area 38 across the FCP 30 as that of the first embodiment. Windows 41 are formed at the intermediate portion so that a portion 39 of the conductors 31 is exposed in its entire width. In the second embodiment, the conductors 31 are contacted with the conductive paths as shown in FIGURES 15 and 16. The adhesive layer 37 on the connection area 36 between the conductors 31 adheres on the printed base plate 34 to fix the posture of the conductors 31 on the conductive paths. The FCP 30 in this embodiment has high reliability in electrical conduction, since the conductors 31 of the FCP 30 are contacted with the conductive paths 35 by merely putting the connection area 36 on the printed base plate and pushing them. Further, this embodiment does not require troublesome soldering work and can improve the connecting work of the FCP. A slight soldering on the exposed conductors 39 does not require reinforcing tape and can improve the mechanical strength of the connection areas. In the above embodiment, the adhesive layer 37 may be a thermoplastic adhesion and the exposed conductors 39 may be omitted. As described above, in the wire harness, it is possible to easily form the crossing and multilayering of the circuit and to eliminate the etching process, since the wire harness comprises the main circuit part, including the insulated conductor wiring circuit plate in which conductors are arranged on the base insulation film to form the wiring circuit, and the branched connection part including the printed wiring plate and the leading electrical wires. It is also possible to readily handle the alternation of the circuit in the wire harness at low cost, since only the main circuit part having the common branched connection part is freely exchanged, and it is possible to reduce the cost for forming the wire harness since the common branched connection part is mass-produced by a standard design and eliminates the etching process. The FCP to be used in the above wire harness can improve conduction to the other elements and electrical reliability, simplify the connecting work, and reduce the cost.

Claims: A wire harness for electrical devices comprising: a main member (1) having a main circuit (7) including an insulated conductor wiring circuit plate (3) in the form of a flexible circuit plate in which conductors (8,31) are arranged on an insulation base film (9, 33) and an upper coverlet film (12, 32) having a back surface with an adhesive layer thereon (11, 37) is disposed on the conductors, and a branch member (2) including a printed wiring plate (4) having a plurality of conductive paths (22) thereon and mounting holes (19) for receiving connector pins of a connector (20) for leading electrical wires (5), wherein a connecting area (14A) is formed by a predetermined width along an edge of said flexible circuit plate being devoid of said insulation base film (9,33) thereby leaving a belt-shaped space across the edge of the flexible circuit plate, and said conductive paths (22) of said printed wiring plate (4) have a side exposed in a connection area (14B) and are directly and electrically contacted in an overlapping relationship in contact with a corresponding one of the conductors (8, 31) on the insulated conductor wiring plate (3) in the connecting area (14A) whereby the adhesive layer on the back surface of the upper coverlet film (32) at positions between the conductors in the belt-shaped space adheres on the printed wiring plate thereby to hold a connection between the flexible circuit plate and the printed wiring plate. A wire harness according to claim 1 in which said connecting area (14A) is formed by the edge of said flexible circuit being devoid of said insulation base film (9,33), and said insulation base film has a front edge which abuts against an opposing edge of the printed wiring plate (3). The wire harness according to claim 2, characterised in that the upper coverlet film (32) includes windows (41) formed therethrough so that upper portions of respective conductors are exposed. A wire harness according to any preceding claim wherein said conductors are wires (8). A wire harness according to any one of the claims 1 to 3, wherein said conductors are strips (31). A wire harness according to any preceding claim, wherein said leading electrical wires (5) are juxtaposed plain electrical wires. A wire harness according to any preceding claim, wherein said insulated conductor wiring circuit plate (3) has a circuit formed by insulator covered conductors (8).

Inventors: FURUTA KOU, HASHIMOTO MASAYOSHI, OKAMURA TAKAHIRO, SAKA KAZUHITO, FURUTA, KOU, HASHIMOTO, MASAYOSHI, OKAMURA, TAKAHIRO, SAKA, KAZUHITO, Furuta, Kou, c/o Sumitomo Wiring Systems, Ltd., Hashimoto, Masayoshi, c/o Sumitomo Wir. Sys., Ltd., Okamura, Takahiro, c/o Sumitomo Wiring Sys., Ltd., Saka, Kazuhito, c/o Sumitomo Wiring Systems, Ltd.
Applicants: SUMITOMO WIRING SYSTEMS, SUMITOMO WIRING SYSTEMS, LTD.
Application year: 1992
Main classification: H01R12
IPC codes: H05K1, H05K3, H01R12, H05K7