| 摘要 |
PURPOSE:To prevent the generation of irregular sound and to enable taking out the maximum output of a motor in an always stable state by causing a piezoelectric element bisected and provided at a ring stator to sweep a driving frequency ranging from a start frequency to the target frequency of the piezoelectric element and also by repeatedly conducting the control of the driving frequency. CONSTITUTION:For the purpose of detecting the abnormal oscillation of a rotor, a monitor electrode 3 is provided between the driving electrodes 2 of a bisected piezoelectric element. Also, a driving signal control circuit is provided with an irregular sound detection means 4 for detecting the abnormal oscillation of the rotor according to the change of a monitor voltage generated from the monitor electrode 3. Further, the irregular sound to be detected by this irregular sound detection means 4 is at a level which cannot be felt by the auditory sense of man. The moment this irregular sound detection means 4 detects allophone, it outputs the detection signal of the irregular sound to a frequency- storing means 5, a sweep time determination means 6 and a frequency determination means 7 to operate these respective apparatus of the driving signal control circuit. |
