PLUNGER POSITION DETECTING DEVICE AND SOLENOID VALVE

PROBLEM TO BE SOLVED: To detect the position of a plunger of a solenoid in an easy method. SOLUTION: The solenoid including a solenoid coil 30 and the plunger 20 employs, as a plunger detecting device which detects the position of the plunger, a convergence time detecting means of detecting a convergence time up to the convergence of a back electromotive voltage generated when the solenoid coil is powered off on a predetermined threshold, a self-inductance calculating means for calculating the self-inductance of the solenoid based upon the convergence time detected by the convergence time detecting means, and a position calculating means for calculating the position of the plunger based upon a value of the self-inductance obtained by the self-inductance calculating means. Consequently, the position of the plunger can be detected with high accuracy by only mere detection processing and calculation processing while the structure is made simple, compact in size, low in cost, and so on. COPYRIGHT: (C)2010,JPO&INPIT