<p>An attraction blade plate is disposed on a plunger of the electromagnet or a cylinder equipped with a single flange and made of a magnetic material is fitted to the axial-direction end portion of a coil bobbin. The change rate of permeance of a magnetic path at the time of attraction can be made great. Attraction retention force is controlled by adjusting the area of the contact surface between the fixed core and a movable core. A permanent magnet is shaped in a toroidal shape and the direction of magnetization is formed in the direction of the thickness of the toroidal shape.</p>
