1. Field of the Invention
The invention relates to an insert-molded product.
2. Description of the Related Art
An electronic control unit for a vehicle has a synthetic resin case with an open upper end. A printed-circuit board is disposed in the case. Electronic circuits and various electronic parts are provided on the circuit board. The electronic control unit further has a cover to close the upper end of the case. Metal nuts are embedded in the case by insert molding and receive screws to fix the cover to the case. The bottom of each nut is held in position during the insert molding by a hold-down pin that projects from the die. However, a hole is formed below the bottom of the nut as the hold-down pin is withdrawn and the bottom of the nut is exposed to the outside of the case. Thus there is a fear that the sealing performance of the case deteriorates.
Japanese Patent Application Laid-Open No. 2004-40945 discloses an electronic control unit for a vehicle that attempts to address the above-described problem. More particularly, a synthetic resin cap is fit on the bottom of the nut. A projection is formed on the outer side surface of the cap and projects in the axial direction of the nut. An edge of the projection and an inner peripheral surface of the die contact each other. Thus, the nut is positioned in the die and the bottom of the nut is not exposed.
Japanese Patent Application Laid-Open No. 2004-40945 proposes insert molding a case partly around a ground wire connection nut, a metal collar and a relay busbar that connects the ground wire connection nut with the metal collar. The case is molded so that the metal collar is in a mounting hole that opens to the outside of a case. Thus, the metal collar and the case can be mounted on a vehicle body. A screw can be threaded into the ground wire connection nut and can connect a ground wire from the electronic circuit in the case to the ground wire connection nut. Another screw or bolt can be passed through the metal collar for mounting the metal collar and the case to the vehicle and for grounding the electric circuit in the case to the vehicle.
The end of the above-described busbar conceivably could be layered on the peripheral edge of the opening of the ground wire connection nut. However, the axial positions of the ground wire connection nut and the other nut then would differ from each other by the thickness of the busbar. However, the caps would require projections of different dimensions corresponding to the depth positions of the nuts. Consequently the cost for manufacturing the insert-molded product is high.
The invention has been completed in view of the above-described situation, and an object of the invention to provide an insert-molded product that can be manufactured at a low cost.