| 摘要 |
PURPOSE:To drive a motor at the most suitable drive frequency by providing a vibrator with a vibration detecting electro-mechanical energy transducer element. CONSTITUTION:The phase difference between an input voltage V1 and an output signal VS of a sensor piezoelectric element 9 is zero degree at frequencies higher than a resonance frequency, gradually increases as the frequency gets nearer to the resonance frequency, becomes 90 degrees at the resonance frequency and increases at frequencies lower than the resonance frequency and gets nearer to 180 degrees. Since a piezoelectric element 3 and the sensor piezoelectric element 9 are positioned in a positional phase difference of zero degree, this phase difference is same in both clockwise and anti-clockwise directions. Therefore, by controlling a frequency so that a phase difference between the input voltage V1 to the piezoelectric element 3 and the sensor piezoelectric element 9 becomes 90 degrees, the frequency can be set at the resonance frequency. |
