Electromagnet and actuating mechanism for switch device, using thereof
An electromagnet includes a coil, a movable iron core adapted to move on the center axis of the coil, and a stationary iron core provided so as to cover the upper and lower surfaces and the outer peripheral surface of the coil. A permanent magnet is arranged in a gap surrounded by the movable iron core and the stationary core.
1. An electromagnet composed of a coil having an upper surface and a lower surface, and an inner peripheral surface, a movable iron core adapted to move on a center axis of the coil, a stationary iron core having an upper end and provided so as to surround the upper and lower surfaces and an outer peripheral surface of the coil, and a power source for applying a current to the coil forwardly and reversely, the movable iron core being moved toward the stationary iron core when the coil is forwardly energized, wherein the stationary iron core includes a stationary core upper member provided so as to cover one axial end of the coil at the upper end of the stationary iron core, and having an inner peripheral surface and an upper surface, a permanent magnet is provided on the upper surface of the stationary core upper member, and the movable iron core is composed of a planar plate member having a surface which is opposed to the upper surface of the stationary core upper member with the permanent magnet intervening therebetween, and a plunger having a distal end part projected from the stationary core upper member and secured to the planar plate which extends above and over the permanent magnet, and having a cylindrical surface opposed to the inner peripheral surface of the coil, the inner peripheral surface of the stationary iron core upper member and the cylindrical surface of the plunger defining therebetween a gap g 1 which is smaller than a thickness of the permanent magnet in the axial direction of the coil in order to prevent a magnet flux produced by the coil from passing through the permanent magnet.
2. An electromagnet as set forth in claim 1 , wherein when a forward current is applied, a magnetic field in the same direction as that of a magnetic field produced by the permanent magnet is produced so as to effect attraction, but when a reverse current is applied, the magnetic field produced by the permanent magnet is cancelled out so as to effect release operation.
3. An electromagnet as set forth in claim 1 , wherein said permanent magnet is selected from a group consisting of a rare earth samarium-cobalt group magnet, a neodymium group magnet, an alnico group magnet and a ferrite group magnet.