压电式蜂鸣器构造与原理介绍.doc

压电式蜂鸣器构造与原理介绍压电蜂鸣片是将高压极压化后的压电陶瓷片黏贴于振动金属片上。当加入交流电压后,会因为压电效应,而产生机械变形伸展及收缩，利用此特性使金属片振动而发出声响。PIEZO BUZZER以回授方式来做区分压电蜂鸣片大致上分为回授式蜂鸣片(自激式)与无回授式蜂鸣片(外激式)两种。当回授式蜂鸣片搭配正回授振荡电路会产生一个与共振腔频率相同的单音；而无回授式蜂鸣片则可以搭配外部振荡电路,选择任意频率发出声音。以下为两种压电蜂鸣片的固定方式:a.外围支持方式-将蜂鸣片外径边缘固定于共振腔内，一般采无回授式蜂鸣片,而其蜂鸣片须与共振腔频率搭配,才会有较高的音压输出,并由外部振荡电路产生推动信号,使蜂鸣器发出声音.b.节点支持方式-将蜂鸣片固定于约与陶瓷片直径同尺寸的环形结构内。若共振腔设计得宜,并搭配频率正确的回授式蜂鸣片与正回授电路,将可产生较大音压及正确的频率。以上两种方式都需以硅胶粘合蜂鸣片于机构中。Piezo buzzer structure and theory introductionPiezoelectoric ceramic buzzer element have a simple structure in which piezoceramic element is glued to vibration plate. When alternating voltage is applied to piezoceramic element, the element expands or shrinks diametrically. This characteristic is utilized to make vibration plated bend to generate sounds.PIEZO BUZZERThe acoustic generating method can be roughly divided into self-drive oscillation method and external-drive oscillation method. The former shows the lowest impedance on the acoustic generator, and produces the sound by the positive feedback oscillation circuit to make resonance. Thereby, big sound pressure can be obtained by a simple circuit. While the latter selects an optional frequency and makes sound by the nonstable multivibrator, and it is used for the case having the oscillation circuit.There are 2 support methods for piezoelectric ceramic buzzers products.a.Circumference Fixing Method-This method is to fix the outside circumference of the buzzer element to the supporting ring of the plate. Considerable sound pressure can be obtained covering a wide frequency range around the resonant frequency.b.Nodal Mounting Method-This Method is to fix the nodal diameter of the buzzer element to the supporting ring of the plate. Loud sound pressure can be obtained. Flexible adhes