超声换能器过固有谐振区匹配理论

超声压电换能器是一个能量转换系统,在超声波振动加工中将超声波电源输出的电能转换为机械振动,由于超声压电换能器是一个容性负载,为保证超声电源输出的电能有效地转换为超声压电换能器的机械振动,需要在超声电源和超声压电换能器之间加一个适当大小的电感进行匹配,但超声压电换能器又是一个强非线性时变系统,在不同的工作频率下其阻抗特性以及机械振动特性差别显著,因此如何将超声压电换能器匹配在一个恰当的工作频率,是提高振动加工质量的关键.通过正确选取超声压电换能器的等效电路模型,并对由此推导出的阻抗圆进行深入分析、研究,可以得出:如将换能器工作频率匹配在大于其内部固有谐振频率的某一频段,可以使换能器振幅最大,振动波形质量也最好,是换能器的最佳工作频段,从而提出超声压电换能器"过固有谐振区"匹配理论.试验结果证明该理论正确.

MATCHING THEORY OF ULTRASONIC TRANSDUCER AT IT'S PASSED INHERENT RESONANCE ZONE

Ultrasonic transducer is an energy transducing system,which can transduce electricity from ultrasonic power to machine vibration in ultrasonic vibration machining.Because ultrasonic transducer is a capacitive load,in order to transduce the electricity energy from ultrasonic power to ultrasonice transducer's machine vibration,it's necessary to add an appropriate inductor between them.On the other hand, ultrasonic transducer is a powerful nonlinear time-varying system,and it's characteristics of impedance and machine vibration differ distinguishingly at different frequency.So,the key of enhancing vibration machining quality is how to match ultrasonic transducer at an appropriate frequency point.By means of rightly selecting ultrasonic transducer's equivalent circuit model and deeply analyzing and researching on the impedance circle induced by it's model,it can be concluded that ultrasonic transducer's vibration amplitude is maximal and it's vibration wave quality is the best when it is matched at it's passed inherent resonance zone.So,the passed inherent resonance zone is the optimal working frequency zone. Consequently,the theory on ultrasonic transducer's matching at it's passed inherent resonance zone is provided.The experiment results show that this theory is true.