Patent ID: 6940376

Claim:
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.