1. Field of the Invention
The present invention relates to a circuit forming method and a circuit connection structure in an electrical connection box for use in a vehicle, for example.
2. Description of the Related Art
In an electrical connection box of the sort mentioned above, an electronic circuit board 104 provided with electronic parts 103 between a lower case portion 101 and an upper case portion 102 constituting the electrical connection box, and an insulating board 106 provided with bus-bars 105 are generally housed in a laminated form as shown in FIG. 5.
The electrical connection of the electronic parts 103 to the bus-bars 105 is accomplished by fitting a connector housing 107 retaining female terminals 108 to an edge portion of an electronic circuit board 104 and stacking the electronic circuit board 104 in this state on top of the insulating board 106 thereby to fit bus-bar tabs (male terminals) 105a with the bus-bars 105 in an upright condition into the respective female terminals of the connector housing 107. An insulating spacer 109 is provided between the electronic circuit board 104 and the insulating board 106 to avoid unnecessary electrical connection.
However, there have been the following problems concerning the connection structure of the bus-bar in the conventional electrical connection box.
(1) When a wiring pattern (not shown) is formed for a number of electronic parts provided on the electronic circuit board 104, it is needed to form the wiring pattern up to the edge portion where the female terminals 108 are provided. Moreover, as a space for use in fitting up the female terminals 108 becomes necessary and this results in a large-sized electronic circuit board 104, thus increasing the cost.
(2) The edge portion of the electronic circuit board 104 requires the female terminals 108 and the connector housing 107 so as to electrically connect the electronic parts 103 to the respective bus-bars 105, so that the number of parts tends to increase.
(3) Moreover, because the bus-bar tab 105a connected to the female terminal 108 is formed by processing the edge portion of the bus-bar 105, any intermediate part of the bus-bar 105 cannot be connected to the female terminal 108 and when one bus-bar is connected to two or more connecting parts, for example, it is needed to use the same number of bus-bars as the number of connecting parts. Consequently, the utilization efficiency of the space for used in arranging the bus-bars has been poor.
An object of the present invention is to solve the foregoing conventional technical problems and to provide a circuit forming method and a circuit connection structure that are capable of making smaller an electronic circuit board as well as reducing the number of parts.
There is provided a circuit forming method in an electrical connection box according to the invention with an electronic circuit board and an insulating board being stacked up and housed therein, comprising the steps of providing not only a through-hole in the electronic circuit board but also lead wires or electric wires of electronic parts in a manner straddling the through-hole, providing the bus-bars on the insulating board so that the upright pressure-contact knife-edges of the respective bus-bars may be arranged in a position corresponding to the through-hole of the insulating board, and stacking up the electronic circuit board and the insulating board by moving both the boards close to each other in such a condition that the pressure-contact knife-edges are passing through the through-hole, and pressure-welding the lead wires or electric wires to the respective pressure-contact knife-edges.
There is provided a circuit connection structure comprising: an electronic circuit board having a through-hole, the electronic circuit board being provided with lead wires or electric wires of electronic parts in a manner straddling the through-hole, and an insulating board provided with bus-bars having upright pressure-contact knife-edges electrically connected to the lead wires or electric wires, wherein the electronic circuit board and the insulating board are stacked up by relatively moving both the boards close to each other in such a condition that the pressure-contact knife-edges are passing through the through-hole; and the lead wires or electric wires are pressure-welded to the respective pressure-contact knife-edges.
As the lead wires are pressure-welded to the respective pressure-contact knife-edges passed through the through-hole provided in the electronic circuit board in this circuit forming method and the circuit connection structure, the space for use in fitting the female terminals to the edge portion of the board in the prior art can be dispensed with, which results in making it possible to reduce the size of the electronic circuit board. Moreover, the pressure-contact knife-edges are directly pressure-welded to the respective lead wires, so that female terminals and the connector housing necessitated in the prior art can be omitted, which results in reducing the number of parts.
In the circuit connection structure according to the invention, the pressure-contact knife-edges are formed separately from the respective bus-bars, and the pressure-contact knife-edges may be fitted to the respective bus-bars in such a condition that the former has been electrically connected to the latter.
With this arrangement, as any number of pressure-contact knife-edges can freely be provided to the end portion or mid position of the bus-bar, the utilization efficiency of the space for use in disposing the bus-bars becomes improvable thereby.