| 摘要 |
PURPOSE:To make it possible to detect the speed of reciprocating movement of a long stroke directly with a high precision, by holding always the density of the leakage magnetic flux at a fixed value in the region where the leakage magnetic flux exists. CONSTITUTION:A leakage magnetic flux is generated between magnetic poles 3a and 3b as shown by the dotted-line arrow in the figure. Here, when displacement corresponding to the speed of a detected object is given to coil 2, Hall element 5 fitted to coil 2 converts the leakage magnetic flux to a voltage according to the moving position. This voltage is compared with the voltage of reference power source 6 by voltage comparator 7, and the deviation voltage is fed back to electromagnets 4a and 4b to increase or reduce exciting currents of electromagnets 4a and 4b, and control is performed until the deviation voltage becomes zero. As the result, even if coil 2 is moved, intensity of the leakage magnetic flux near coil 2 is always held at a set fixed value. Thus, the speed of reciprocating movement of a long stroke can be detected directly with a high precision. |
