SOLENOID

PROBLEM TO BE SOLVED: To stabilize the actuation of a plunger and reduce the operating sound of the plunger in a solenoid used for the shift-lock mechanism etc., of AT vehicles. SOLUTION: The solenoid attracts the plunger 3 composed of a magnetic material against the energizing force of a coil spring 2 when a current is passed in a coil 1 and returns the plunger 3 to the original position by means of the energizing force of the coil spring 2 when the current flow in the coil 1 is stopped. The coil spring 2 exhibits such nonlinear energizing force characteristics that the energizing force of the spring 2 in its intermediately contracted state becomes weaker than the linear reversely proportional relation between the contracted length and energizing force of the spring 2. In order to realize the characteristics of the coil spring 2, the winding pitch of the spring 2 is made coarse at the central part of the spring 2 and dense at both ends of the spring 2 and their vicinities. Consequently, the actuation of the plunger 3 can be stabilized and the operating sound of the plunger 3 can be reduced. COPYRIGHT: (C)2005,JPO&NCIPI