| 摘要 |
PROBLEM TO BE SOLVED: To drive by a drive pulse having a set frequency range and waveform, by setting to respectively satisfy specific formulae at a frequency and wavelength of the pulse. SOLUTION: A drive pulse generated from a drive pulse generating means has a sawtooth drive pulse having a slow speed change part and a fast change part. Its frequency (f) is set to satisfy a formula (1). And its wavelength T is set to a range for satisfying formulae (2), (3) and (4), where fr is a resonance frequency of an electro-mechanical converter, T1 is a width of the drive pulse, T2 is a width of the slow speed change part of the pulse voltage, and T3 is a width of the fast speed change part. The drawing shows the case that the frequency (f) of the pulse is 35 kHz slightly lower than 2/3 of the resonance frequency. A region (a) is a range of 75 to 100% of a driving speed to a maximum speed of the case of 35 kHz., a region (b) is a range of 50 to 75%, and a region (c) is a range of 25 to 50%. |
