Patent Publication Number: US-2002006742-A1

Title: Terminal box

Description:
FIELD OF ART  
       [0001] The present invention relates to an electrical connection box installed in a vehicle, for example, in an engine room of an automobile and the like and used for connection of a wiring harness and the like.  
       BACKGROUND ART  
       [0002] As the demand for amenity in driving increases, a vehicle, for example, an automobile tends to be equipped with a larger number of electrical devices and apparatuses such as an audio apparatus, a navigation apparatus, a television apparatus, an electrical antenna, an air conditioner, a rear window heater, a seat heater, a power seat, a suspension hardness control and the like.  
       [0003] To those on-vehicle electrical devices and apparatuses, power is supplied using wiring harnesses or the like via an electrical connection box placed near a battery in an engine room. The electrical connection box contains electrical components such as fuses for preventing excessive current flowing when a short circuit is produced between the wiring harnesses or the like and a body due to some trouble or when a load such as a motor breaks down, and relays operating in association with various control switches to control power supply to the on-vehicle electrical devices or apparatuses.  
       [0004] There is known an electrical connection box wherein, in view of heat emission, circuits of desired shapes are formed by bus bars and arranged between distribution boards, and fuses and relays are attached to the circuits, for example, from Japanese Unexamined Patent Publication (KOKAI) No.  59-28818.    
       [0005] Each bus bar is formed by stamping out a desired circuit shape from an electrical conductive plate of copper, copper alloy, brass or the like and then bending the stamped-out shape. The electrical circuits are formed by arranging the bus bars in a manner that they do not touch each other.  
       [0006] The electrical connection box using bus bars comprises many components. Therefore, it is difficult to downsize the electrical connection box. The production thereof needs many dies because in addition to stamping dies for bus bars, dies for molding synthetic resin into insulating spacers, which are arranged between bus bars and between a case and bus bars, are also needed. Therefore, cost of dies is large. Further, because of using many dies, it is difficult or practically impossible to modify the design of the electrical connection box.  
       [0007] In the engine room of an automobile in which the electrical connection box is to be installed, free space is very limited because many on-vehicle components are installed therein. In addition, the number of on-vehicle electrical devices and apparatuses tends to increase as stated above. Therefore, in order to save space, the design of the electrical connection box needs to take account of wiring between the electrical connection box and on-vehicle electrical devices and apparatuses.  
       [0008] Thus, there is a demand for an electrical connection box for an automobile which can be downsized keeping a heat emitting property equivalent to that of the electrical connection box using bus bars.  
       [0009] The present invention has been made in view of the above problems. The object thereof is to provide an electrical connection box which takes account of wiring to on-vehicle electrical devices and apparatuses, exhibits a heat emitting property equivalent to that of an electrical connection box using bus bars, and can be downsized.  
       Disclosure of the Invention  
       [0010] In order to attain the above object, the present invention provides an electrical connection box having a circuit board contained in a case, wherein the circuit board is divided in accordance with power supply systems.  
       [0011] It is desirable that the electrical connection box is installed in an automobile and the circuit board is divided into one for a power supply system for start and travelling of the automobile and one for a power supply system for general loads.  
       [0012] It is desirable that the circuit board comprises a metal plate as a core. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0013]FIG. 1 is an exploded perspective view of an electrical connection box of the present invention; FIG. 2 is a perspective view showing how circuit boards are contained in a case of the electrical connection box of FIG. 1; FIG. 3 is an enlarged cross-sectional view of a circuit board shown in FIG. 2; FIG. 4 is a circuit diagram showing an example of an electric system of an automobile in which the electrical connection box of FIG. 1 is installed; FIG. 5 is a perspective view of another modified example of circuit boards to be contained in the case of the electrical connection box of FIG. 1; FIG. 6 is an exploded perspective view of another embodiment of the electrical connection box of the present invention; and FIG. 7 is a cross-sectional view of a circuit board for use in the electrical connection box of FIG. 6. 
    
    
     Best Mode of Carrying out the Invention  
     [0014] As an embodiment of the present invention, an electrical connection box to be installed in an engine room of an automobile will be described in detail referring to FIGS.  1  to  7 .  
     [0015] As shown in FIG. 1, an electrical connection box  1  comprises an upper cover  2 , a lid  3 , a board unit  4 , a case  5  and a lower cover  6 . The upper cover  2 , the lid  3 , holding members  43  (described later) of the board unit  4 , the case  5  and the lower cover  6  are molded from synthetic resin, particularly from synthetic resin having a good electrical insulating property (nylon, PBT(polybutylene terephthalate), PP(polypropylene) or the like).  
     [0016] The upper cover  2  is to prevent water from coming into the electrical connection box  1 .  
     [0017] The lid  3  is put on the top of the case  5 . The lid  3  is provided with openings  3   a  of various shapes in which terminals  44   a ,  45   a  of various fuse holders  44 ,  45  (described later) are set. Thus, the lid  3  doubles as a holder for fuses which are replaceable components.  
     [0018] As shown in FIG. 2, the board unit  4  comprises circuit boards  41 ,  42  having a good heat emitting property and two holding members  43 , which are assembled into a unit.  
     [0019] A plurality of slow blow fuse holders  44 , mini fuse holders  45 , relays (not shown) and/or the like are attached to the circuit boards  41 ,  42 , and the circuit boards  41 ,  42  are spaced apart and held by the holding members  43  on both sides. Each holding member  43  has a guide groove  43   b  on its outside surface  43   a , and a plurality of pins  43   c  on both sides thereof. The guide groove  43   b  is provided to help insert the board unit  4  into the case  5 . The pins  43   c  are provided to fit in location holes  41   f ,  42   f  (described later) of the circuit boards  41 ,  42 .  
     [0020] The slow blow fuse holders  44  and mini fuse holders  45  are different in shape. They are provided to connect mini fuses (downsized blade fuses) (not shown) and slow blow fuses (not shown) electrically and mechanically to their related circuits formed on the circuit boards  41 ,  42 . The mini fuses and slow blow fuses are provided to prevent excessive current flowing when a short circuit is produced between a wiring harness or the like and a body or when a load such as a motor breaks down. The slow blow fuse holders  44  and mini fuse holders  45  are provided with terminals  44   a ,  45   a . The above mentioned relays are provided to operate in association with various control switches to control power supply to on-vehicle electrical devices and apparatuses.  
     [0021] Since the circuit boards  41 ,  42  have the same structure, only the structure of the circuit board  41  will be described. The description of the structure of the circuit board  42  will be omitted.  
     [0022] In order to have a good heat emitting property, the circuit board  41  has, for example, a structure shown in FIG. 3, wherein a metal plate  41   a  of aluminum, aluminum alloy, copper or copper alloy having a thickness of 0.2 to 1.2 mm is coated with an insulating layer  41   b , and on the surface of the insulating layer, an electrical conductive layer  41   c  of copper foil and an electrical insulating resist layer  41   d  each having a thickness of 50 to 120 μm form conductive patterns of desired shapes. Through-holes  41   e  and location holes  41   f  (FIG. 2) are formed in the circuit board  41  at appropriate positions.  
     [0023] If the heat emitting property of the circuit board  41  is improved by forming the insulating layer  41   b  from adhesive insulating prepreg to which alumina powder or the like is added, the conductive patterns are allowed to have a smaller width for the same current capacity. This helps downsize the electrical connection box  1  further.  
     [0024] In the case of the circuit boards  41 ,  42 , heat collected by the metal plate  41   a  is discharged from the electrical connection box  1  by being transferred via metal brackets (not shown) to an external portion and by being radiated from the case  5  and the metal brackets. If the metal brackets are fixed directly to a body of an automobile, heat. is transferred directly to the body, so that heat discharge is improved. If heat emitting members such as micro heat pipes are attached to the metal brackets, heat discharge is further improved.  
     [0025] The electrical connection box  1  of the present invention is characterized in that two circuit boards are each assigned to one power supply system, that is, the circuit board  41  is assigned to a power supply system for start, traveling and the like of an automobile, and the circuit board  42  is assigned to a power supply system for general loads.  
     [0026] An example of an electrical system of an automobile in which an electrical connection box  1  of the present invention is installed will be described based on FIG. 4. The electrical connection box  1  is connected to an alternator  10 , an on-vehicle battery  11  and a fusible link box (hereinafter referred to simply as “link box”)  12  via wires  13  such as wiring harnesses or the like.  
     [0027] Here, power for start, traveling and the like of an automobile, for example, power for a starter motor, hazard lamps, turn signal lamps, a horn and the like is supplied from the on-vehicle battery  11  to a circuit board  41  of the electrical connection box  1 , while power for general loads, for example, power for accessories such as heaters for removing a blur on mirrors by heating, an audio apparatus, a seat heater and the like is supplied from the alternator  10  and the on-vehicle battery  11  to a circuit board  42 .  
     [0028] A case  5  is a member of a rectangular tube shape for containing a board unit  4 , and protrusions  5   a  are formed on the inside thereof at positions corresponding to guide grooves  43   b  of holding members  43  so that the protrusion  5   a  may be inserted in the guide grooves  43   b . The case  5  may be made of aluminum alloy or the like in view of heat emission.  
     [0029] A lower cover  6  is attached to cover the bottom of the case  5 . It is provided with an opening  6   a  from which cables are to be drawn.  
     [0030] The electrical connection box  1  of the above described structure is assembled by inserting the board unit  4  in the case  5 , attaching a lid  3  and the lower cover  6  to cover the top and the bottom of the case  5 , respectively, and setting an upper cover  2  on the lid  3 , as shown in FIG. 1.  
     [0031] The assembled electrical connection box  1  has the separate circuit boards  41 ,  42  assigned to the power supply system for start and traveling of the automobile and the power supply system for general loads, respectively. Therefore, on-vehicle apparatuses and devices can be divided between the two circuit boards  41 ,  42 , and wiring between the electrical connection box  1  and the on-vehicle apparatuses and devices can be shorter and simpler. Further, because of the use of the circuit boards  41 ,  42 , the electrical connection box  1  can be downsized to such an extent that the volume thereof is one-third to half as large as the volume of a conventional electrical connection box using bus bars, keeping a heat emitting property equivalent to that of the conventional electrical connection box.  
     [0032] It may be so arranged that a plurality of connectors are provided in accordance with destinations of wiring harnesses and attached to circuit boards divided in accordance with power supply systems so that wiring harnesses having the same destination may be connected in a lamp, as in the case of circuit boards  51 ,  52  shown in FIG. 5.  
     [0033] Specifically, a circuit board  51  is a board to which power for start, traveling and the like of an automobile, for example, power for a starter motor, hazard lamps, turn signal lamps, a horn and the like is supplied from an on-vehicle battery  11 , and it has a structure similar to that of the circuit board  41 . As shown in FIG. 5, a male connector  53  having three receiving openings  53 a to  53 c (reference signs  53 b and  53 c are not shown) is attached to the circuit board  51  at its edge portion on its upper side (as viewed in FIG. 5).  
     [0034] A circuit board  52  is a board to which power for general loads, for example, power for accessories such as heaters for removing a blur on mirrors by heating, an audio apparatus, a seat heater and the like is supplied from an alternator  10  and the on-vehicle battery  11 , and it has a structure similar to that of the circuit board  42 . As shown in FIG. 5, a male connector  54  having three receiving openings  54   a  to  54   c  is attached to the circuit board  52  at its edge portion on its lower side (as viewed in FIG. 5).  
     [0035] To the circuit boards  51 ,  52 , first, second and third female connectors  56 ,  57 ,  58  are attached in a manner that they fit in their corresponding receiving openings  53   a  and  54   a ,  53   b  and  54   b ,  53   c  and  54   c , respectively, to thereby bridge the male connectors  53 ,  54 .  
     [0036] To the female connectors  56  to  58 , connectors provided at the ends of wiring harnesses are connected in accordance with their destinations in terms of electrical systems. The female connectors  56  to  58  also connects the circuit boards  51 ,  52 . The female connectors  56  to  58  have a plurality of receiving holes  56   a  to  58   a  in which female terminals (not shown) are to be fitted. Thus, the wiring harnesses (not shown) having various destinations extend from behind the female connectors  56  to  58 .  
     [0037] With the arrangement that the connectors provided at the ends of the wiring harnesses are connected to the female connectors  56  to  58  in accordance with their destinations in terms of electrical systems, the circuit boards  51  and  52  are connected with each other, and the wiring harnesses having the same destination in terms of electrical systems are connected in a lamp. Therefore, the number of connectors are reduced, and connecting members for connecting the circuit boards  51 ,  52  are not needed any longer.  
     [0038] An electrical connection box may have a structure described below, wherein a circuit board described below is used instead of the circuit boards  41  and  42  or circuit boards  51  and  52 .  
     [0039] As shown in FIG. 6, an electrical connection box  60  comprises an upper case  61 , a lower case  62  and a circuit board  63 .  
     [0040] The upper case  61  has an insertion housing  61   a  formed on one side thereof, and a connector housing  61   d  formed at the center thereof. In the insertion housing  61   a , a relay insertion hole  61   b  and a fuse insertion hole  61   c  are formed. There lay insertion hole  61   b  has a rectangular cross-section corresponding to the cross-section of a relay  65 , and the fuse insertion hole  61   c  has a rectangular cross-section corresponding to the cross-section of a fuse  66 . The connector housing  61 d has a frame-like shape to hold connectors of wiring harnesses or the like. The connector housing  61 d is provided at a position corresponding to terminals  63   g  for male connectors (described later) provided on the circuit board  63 .  
     [0041] The lower case  62  is arranged opposite to the upper case  61  with the circuit board  63  interposed therebetween. The lower-case  62  has ribs  62  at its four corners of the bottom for use in positioning the circuit board  63  in the vertical direction. Each rib  62   a  has a screw hole  62   b  formed on its upper side.  
     [0042] The circuit board  63  is a printed circuit board mainly made of glass epoxy resin which is generally used for an electronic unit. As shown in FIG. 7, the circuit board  63  comprises a metal plate  63   a  as a core, an insulating layer  63   b  which covers the surface of the metal plate  63   a , an electrical conductive layer  63   c  formed on the insulating layer  63   b , and a resist layer  63   d  formed on the electrical conductive layer  63   c.    
     [0043] The material of the metal plate  63   a  needs to be able to impart rigidity to the circuit board  63 , but it is not restricted to any special one. A plate of aluminum, aluminum alloy, copper, copper alloy, iron or the like may be used for the metal plate  63   a . Since aluminum, aluminum alloy, copper, copper alloy and the like have a high thermal conductivity, the metal plate  63  made of any of those materials can transfer the heat caused by heating of electrical components such as a relay  65 , to the outside. Thus, a rise in temperature occurring locally in the metal plate  63  can be restrained. Among the above materials, aluminum is the most favorable for the metal plate  63   a , because use of aluminum helps make the circuit board  63  light and improves the heat emitting property thereof, and it is easy to form holes in a plate of aluminum. It is favorable that when the plate  63   a  is an aluminum plate, it is 0.2 to 2.0 mm in thickness. Specifically, in view of improving the heat emitting property, the aluminum plate having a thickness of 0.5 mm or more is favorable. In view of making it easier to form holes, the aluminum plate having a thickness of 1.0 mm or less is favorable.  
     [0044] The insulating layer  63   b  is made of prepreg of glass fabric impregnated with epoxy resin, and covers the surface of the metal plate  63   a . If epoxy resin to which alumina power or the like is added is used for the insulating layer  63   b , thermal conductivity thereof is improved. The electric conductive layer  63   c  is, for example, made of copper foil having a thickness of 18 to 210 μm, and forms predetermined circuit patterns on the insulating layer  63   b . The resist layer  63   d  is a coat of epoxy or the like provided to prevent oxidation and soldering of the electrical conductive layer  63   c.    
     [0045] As shown in FIG. 7, through-holes  63   e  are formed in the circuit board  63  at predetermined positions. Each through-hole  63   e  is coated with an electrolytic copper coat  63   f , which connects the circuit patters formed by the electric conductive layer  63   c  on the face and back sides of the circuit board  63 .  
     [0046] The circuit board  63  is produced, for example, as follows:  
     [0047] First, holes having a size a little larger than the size of to-be-formed through-holes  63   e  are formed in a metal plate  63   a  at positions predetermined for the through-holes  63   e.    
     [0048] Next, a layer of prepreg of glass fabric impregnated with epoxy resin is formed on both sides of the metal plate  63   a , and an electrical conductive layer  63   c  of copper foil is formed on the layer of prepreg. Then, the metal plate  63   a  with the layer of prepreg and the electrical conductive layer  63   c  is subjected to pressure pressing in a vacuum heating furnace and thereby formed into a flat board. In this step, part of the epoxy resin with which glass fabric is impregnated melts, and the holes formed in the metal plate  63   a  are filled with the melted epoxy resin.  
     [0049] Then, the through-holes  63   e  are formed at the above mentioned predetermined positions, and the inside of each through-hole  63   e  is coated with an electrolytic copper coat  63   f.    
     [0050] Then, desired circuit patterns are formed by patter etching, and last, a resist layer  63   d  is formed. Since the insulating layer of synthetic resin (for example, epoxy resin) is formed between the coat  63   f  and the metal plate  63   a  inside the through-hole  63   e , insulation is ensured.  
     [0051] As shown in FIG. 6, on the circuit board  63 , terminals  63   g  for male connectors are arranged at an appropriate position, for example, at the center, and terminals  63   h  on which a relay  65  is to be mounted and male terminals  63   j  for a fuse on which a fuse  66  is to be mounted are arranged at an end portion. Further, through-holes  63   k  are formed in the circuit board  63  at its four corners corresponding to the screw holes  62   b  of the lower case  62 .  
     [0052] In this embodiment, two or more circuit boards  63  may be laid with an insulating material therebetween. The circuit board  63  may also have a structure wherein thin glass epoxy boards are laid on both sides of a core metal plate  63   a  with an insulating layer interposed.  
     [0053] The electrical connection box  60  of the above described structure is assembled as follows:  
     [0054] First, the circuit board  63  is placed on the ribs  62   a  of the lower case  62 , and fastened to the ribs  62  by screws. Then the upper case  61  is set on the lower case  62 , and the upper and lower cases are joined.  
     [0055] Then, for example, a plug-in type ISO relay  65  is inserted in the relay insertion hole  61   b  and connected to the terminals  63   h  on the board, and, for example, a fuse  66  for medium current (MC) is inserted in the fuse insertion hole  61   c  and connected to the male terminals  63   j  for a fuse. Thus, the electrical connection box  60  is assembled.  
     [0056] By inserting connectors (not shown) of wiring harnesses in the connector housing  61   d  of the assembled electrical connection box  60 , electrical connection between on-vehicle electrical devices and apparatuses and a battery is established.  
     [0057] Since the electrical connection box  60  uses a relatively rigid aluminum plate as a core of the circuit board  63  contained therein, deflection of the circuit board  63  which tends to occur when a relay, a fuse or a connector of a wiring harness is attached to or detached from the circuit board is restrained. Therefore, separation of soldering portions which tends to occur with the deflection of the circuit board  63  is restrained, and electrical connection defectives are reduced. Ribs other than the ribs at the four corners, which used to be provided at the bottom of the lower case  62  for preventing the deflection of the circuit board, are not needed any longer. This makes the production of the lower case  62  easier.  
     [0058] By using the electrical connection box of the present invention, larger free space can be obtained in an engine room. Therefore, for example, a circuit board (a glass epoxy board will do) comprising a signal circuit for a CPU or the like may be installed in the free space, depending on the destination or grade of an automobile.  
     [0059] Further, for example, if through-holes are formed in the circuit boards  41 ,  42  and the metal plates  41   a ,  42   a  are connected by a conductor, the metal plates can serve as conductors. Thus, for example, the circuit boards  41 ,  42  can be electrically connected, and earth current can be made flow through the circuit boards  41 ,  42  to a vehicle body side.  
     Industrial applicability  
     [0060] According to the first aspect of the present invention, there is provided an electrical connection box which takes account of wiring to on-vehicle electrical devices and apparatuses, keeps a heat emitting property equivalent to that of an electrical connection box using bus bars, and can be downsized.  
     [0061] According to the second aspect of the present invention, the electrical connection box is installed in an automobile, and the circuit board is divided into one for a power supply system for start and traveling of the automobile, and one for a power supply system for general loads. With this structure, wiring to on vehicle electrical devices and apparatuses can be shorter and simpler.  
     [0062] According to the third aspect of the present invention, a metal plate is used as a core of a printed circuit board. Therefore, deflection of the printed circuit board which tends to occur when a relay, a fuse or a connector of a wiring harness is attached to or detached from the printed circuit board is restrained. Therefore, occurrence of troubles such as separation of soldering portions from the circuit board due to a load thereon and connection defectives caused by such separation is restrained. Thus, reliability of the electrical connection box is improved.  
     [0063] Further, in the electrical connection box according to the third aspect which can restrain the deflection of the printed circuit board, the number of ribs, which used to be provided at predetermined positions on the lower case in order to prevent the deflection of the printed circuit board, can be reduced. Thus, work needed for mounting the printed circuit board is reduced, the printed circuit board can be designed with wider freedom, dies for cases can be designed more easily, and production cost of the electrical connection box can be reduced.