A conventional multidirectional operation switch disclosed in Japanese Patent Laid-Open Publication No. 11-31440 will be described with reference to FIGS. 8 to 12. FIG. 8 is an exploded perspective view of the conventional multidirectional operation switch. FIG. 9 is a plan view of a case of the conventional multidirectional operation switch. FIG. 10 is a sectional view taken along line 10—10 of the multidirectional operation switch shown in FIG. 9. Case 1 made of insulation resin has a substantially square shape seen from its upper surface, and has a recess opening upward. Central fixed contact 2A is provided at the center of a bottom of the recess of case 1. Two outer fixed contacts 2B are provided at the periphery of the recess symmetrically with respect to each other about central fixed contact 2A. Inner fixed contacts 2C are arranged at the recess in eight directions at equal angular intervals from central fixed contact 2A between central fixed contact 2A and outer fixed contacts 2B. Four of inner fixed contacts 2C are located along directions from central fixed contact 2A to corners of case 1, and other four inner fixed contacts 2C are located between the four inner fixed contacts. Five terminals, i.e., terminal 8B and terminals 8C led out independently from one of outer fixed contacts 2B and four of inner fixed contacts 2C are aligned on outer side surface 1B of case 1. Similarly, five terminals, i.e., terminal 8B and terminals 8C led out independently from other of outer fixed contacts 2B and other four inner fixed contacts 2C are aligned on outer side surface 1C opposite to outer side surface 1B. As shown in FIG. 9, terminal 8A led out from central fixed contact 2A passes from the center of the recess of case 1 through between two of inner fixed contacts 2C and is provided on outer side surface 1A, which is different from the outer side surfaces 1B and 1C.
Movable contact 3 having a circular dome-shape and made of resilient metallic thin plate is accommodated in the recess of case 1, and has a peripheral lower edge mounted on outer fixed contact 2B. Hole 3A is formed at a central top portion of movable contact 3 and is larger than the outer diameter of central fixed contact 2A. Hole 3A faces central fixed contact 2A.
Operation body 4 made of insulation material includes operation shaft 4A and flange 4B which are unitarily formed with each other. Operation shaft 4A protrudes upward and has a substantially quadrangular cross section in a direction perpendicular to a direction in which the dome shape of movable contact 3 protrudes. Flange 4B is located below operation shaft 4A. Rivet portion 5 made of conductive material is attached to the lower portion of flange 4B.
A lower flat portion 5A of rivet portion 5 has a circular shape seen from upside. The circular shape of the lower flat portion 5A has a radius larger than a distance from central fixed contact 2A to inner fixed contact 2C. That is, central fixed contact 2A and inner fixed contact 2C are located below the lower flat portion 5A.
The lower surface of lower flat portion 5A of rivet portion 5 contacts the upper surface of the periphery of hole 3A of movable contact 3. Flange 4B of operation body 4 to which rivet portion 5 is attached is accommodated in the recess of case 1. An edge of lower flat portion 5A of rivet portion 5 is located substantially above inner fixed contacts 2C.
Cover 6 made of metal plate has bearing portion 6A having a substantially quadrangular at its central portion and holds operation body 4 so that operation shaft 4A of operation body 4 protrudes through bearing portion 6A. Cover 6 is attached to case 1 so as to cover the recess of case 1, so that each side of bearing portion 6A is in parallel to each side of the periphery of case 1.
An upper surface of flange 4B of operation body 4 contacts the lower surface of cover 6. That is, flange 4B of operation body 4 to which rivet portion 5 is attached is located between the lower surface of cover 6 and the upper surface of movable contact 3. In an ordinary state shown in FIG. 10, an operation force is not applied to operation shaft 4A, and operation body 4 keeps a neutral position perpendicular to the bottom of the recess of case 1. Operation knob 7 is placed at the upper end portion of operation shaft 4A of operation body 4.
An operation of the multidirectional operation switch configured as mentioned above will be described. FIGS. 10 to 12 are sectional views of the conventional multidirectional operation switch.
As shown in FIG. 10, when operation body 4 is in a neutral position and an operation force is not applied to operation shaft 4A, the switch is in a ordinal state in which any of outer fixed contacts 2B, inner fixed contacts 2C, and central fixed contact 2A do not contact each other. Inner fixed contacts 2C do not contact.
As shown in FIG. 11, the left side of the upper surface of operation knob 7 placed at the upper end portion of operation shaft 4A of operation body 4 is depressed in direction D11, and operation body 4 accordingly tilts with respect to the right side of the upper end portion of flange 4B, a fulcrum. Then, the left side of edge 5A1 of lower flat portion 5A of rivet portion 5 fixed to the lower surface of the flange 4B presses the left side of the upper surface of movable contact 3 above inner fixed contact 2C located at the left side. Simultaneously to this, the portion of movable contact 3 partly bends and generates a click feeling. Then, inner fixed contact 2C arranged at the left side and outer fixed contact 2B are electrically connected via movable contact 3, and thereby, predetermined terminals 8C and 8B corresponding to fixed contacts 2C and 2B are electrically connected. At this moment, since the central top portion of movable contact 3 has the hole larger than central fixed contact 2A, central fixed contact 2A does not contact movable contact 3. Since rivet portion 5 attached to the lower surface of flange 4B tilts together with flange 4B of operation body 4, rivet portion 5 does not contact central fixed contact 2A.
Then, when the force applied to operation knob 7 is removed, movable contact 3 restores its original shape by a restoring force of the contact and departs from inner fixed contact 2C arranged at left side mentioned above. Then, operation body 4 is pushed back to the original, neutral position, so that the fixed contacts do not contact, as shown in FIG. 10.
Similarly, when a position of operation knob 7 on operation body 4 corresponding to inner fixed contacts 2C is pushed, inner fixed contact 2C corresponding to the position and outer fixed contact 2B are electrically connected, thereby allowing terminals 8C and 8B corresponding to the fixed contacts to be electrically connected. When the pressing force is removed, the switch returns to the ordinal state shown in FIG. 10.
As shown in FIG. 12, when operation body 4 is pressed with a pressing force applied from the central upper surface of operation knob 7 in direction D2, i.e., from an upper side to a lower side, lower flat portion 5A of rivet portion 5 fixed to flange 4B of operation body 4 presses the central portion of movable contact 3. Thereby, movable contact 3 entirely inverts, generating a click feeling. Simultaneously to this, the center of lower portion of the lower flat portion 5A of rivet portion 5 contacts central fixed contact 2A exposing through hole 3A of movable contact 3. As a result, central fixed contact 2A and outer fixed contacts 2B are electrically connected via movable contact 3 contacting rivet portion 5, thus allowing terminals 8A and 8B corresponding thereto to be electrically connected.
Then, when the pressing force is removed, operation body 4 is pushed up by a restoring force of movable contact 3, so that the switch returns to the state shown in FIG. 10, in which the switch are turned off.
In the conventional multidirectional operation switch, two outer fixed contacts 2B, eight inner fixed contacts 2C for tilting operation and central fixed contact 2A for pushing operation are arranged on the bottom of the recess of case 1. In order to lead out terminal 8A from central fixed contact 2A, it is necessary to lead out the terminal 8A through between two of inner fixed contacts 2C arranged in the eight directions at the equal intervals. The switch is recently demanded to have a small size to provide small and thin apparatuses, and the intervals between the contacts become narrow accordingly, thus limiting the small size. Terminal 8A may be led out from central fixed contact 2A to a position different from the positions of the other terminals in the thickness direction of case 1. However, in this case, since portions where terminals are led out cannot be formed in one plane, processes are likely to be complicated. Further, case 1 has a large thickness accordingly, and thus, it is difficult to make the switch thin.