1. Field of the Invention
This invention relates to a structure of a contact point of a terminal piece which is used principally for a switch, such as an ignition switch for a vehicle, and to a production method for the structure thereof.
2. Description of the Prior Art
There has been known a structure of a contact point of a terminal piece and a production method for the terminal piece, as shown in FIGS. 8 and 9 (see Japanese Laid-open Utility Model Publication No. Sho 62-98125).
In FIGS. 8 and 9, each of the terminal pieces 1 has a platelike leg portion 4 which is inserted into and connected to each of connector slits 3 of a corresponding connector 2.
The terminal piece 1 further has a base plate portion 5 extending from the leg portion 4. The base plate portion 5 has substantially the same thickness as that of the leg portion 4 and is formed integrally with the leg portion 4 by bending a single copper plate substantially perpendicularly.
The base plate portion 5 is brought into contact with or separated from a contact point plate 10 on a movable side which functions as another terminal contact point, so that an electric signal is passed or shut off electrically.
By pressing, the base plate portion 5 is provided with a contact point 6 shaped substantially into a hat in section which expands in a direction in which the leg portion 4 extends, in other words, expands toward the movable-side contact point plate 10.
The contact point 6 has a top portion 7, which can come into contact with the movable-side contact point plate 10, and a circumferential wall portion 8 formed around the top portion 7.
The thus formed terminal pieces 1 are buried and fixed in an insulating bass 9 by, for example, insert forming.
The movable-side contact point plate 10 is attached to a rotor 12 disposed rotatably in a cylindrical case 11.
The rotor 12 is rotated along with an ignition key (not shown), and thereby movable contact points 13, 13 attached to the movable-side contact point plate 10 are brought into contact with or separated from the top portions 7, 7 of the contact points 6, 6, respectively. Accordingly, various modes of positionings, such as turn-on, turn-off, starting, or electrical continuity in accessories, are performed.
However, in this conventional structure of the contact point of the terminal piece and the production method for it, the top portion 7 of the contact point 6 is spread out when being formed by pressing.
Therefore, there is a fear that the top portion 7 will be formed thinner than the base plate portion 5 therearound and accordingly abrasion caused by a repetition of the contact and separation of the top portion 7 with and from the movable contact point 13 will lower the durability of the top portion 7.
In order to solve this problem, it might be a possible solution to heighten the durability of the top portion 7 by increasing the thickness of the base plate 5 and the leg portion 4 approximately 2 to 2.5 times.
However, this method brings about a rise in material cost for increasing the thickness of a copper plate used as metallic materials and a rise in processing costs for bending the leg portion 4 and the base plate 5 or forming the leg portion 4 so as to be inserted into the connector slit 3 of the connector 2.