| 摘要 |
PURPOSE:To dispense with a return spring, which may cause fatigue failure, and provide a contactless structure with long service life and high reliability by relatively moving a superconductive material and a key top with respect to a permanent magnet, and raising the key top by the Meissner effect of magnetic flux generated in the permanent magnet. CONSTITUTION:A permanent magnet 8 and a detecting coil 9 are arranged in a frame 10 in opposition to a superconductive material 7. The superconductive material 7 is usually held in the raised state by the Meissner effect of magnetic flux generated in the permanent magnet 8. In the case of pushing down a key top 5 by a finger, the superconductive material 7 lowers, while in the case of its release, the superconductive material 7 returns in the raised state by the Meissner effect. Thereat, change in the magnetic flux generated in the permanent magnet 8 induces superelectric power to the detecting coil 9. A detecting circuit 11 receives and processes the superelectric power so as to obtain a key pushing-down signal and a key releasing signal. The detecting circuit 11 also processes the peak level of voltage in the superelectric power generated in the detecting coil 9 so as to enable the detection of key touch speed, thereby effectively utilizing this device as a key board for an electronic musical instrument. |
