02-4东莞思威特电子-压电水声换能器的应用

思威特电子-压电换能器在声纳系统中应用Sonarfordetection声纳，是英语“声导航和定位”的缩写。利用水下声波的传播的规律进行水中目标的观察和通讯的系统成为声纳系统。声纳系统应在民用方面有测深仪器、多波束深仪器，海底底层剖面仪和多普勒导航声纳等，在军事上，舰用主动、被动声纳，拖拽可变深度声纳、拖拽线列声纳、直升飞机吊放声纳、定位、跟踪、浮标声纳等等。压电声纳在两次世界大战和民用方面，发挥了重要作用。Sonarisshortfor“SoundNavigationAndRanging”.Thesystemthatutilizesthepropagatinglawsofunderwatersoundwavetoobserveandcommunicatethetargetinwaterdefinesassonarsystem.Forciviluse,itcoverssoundingapparatus,multi-beamdeepinstrument,oceanbottomprofilerandDopplernavigationsonaretc.Formilitaryuse,itcoversactiveandpassivesonarusedinwarship,towedvariable-depthsonar,towedarray-linersonar,helicopter-dunkedsonar,fixedsonar,trackingsonarandsonobuoyetc.最早使用于鱼群探测仪的郎之万型换能器，是外径为60mm,，厚度为5mm的压电陶瓷片与厚度为14mm的两个钢柱粘结而成的，重量约为700克，谐振频率为50KHz。当把它作为发射、接收换能器使用时，其实际结构图如图2所示。它是用橡胶把换能器与电缆包封起来。声波通过厚度约为1cm的透声橡胶向水中辐射信号（橡胶一起的损失仅为1dB，影响可以忽略）;辐射面以外的换能器部分均用海绵橡胶包封，使声波仅向一个方向辐射。Langevintransducerconsistsofpiezoelectricceramicthatis60mmindiameterand5mminthicknessandtwosteelcolumnsthatis14mminthickness,itis700graminweightand50KHzinresonantfrequency,whichisfirstlyusedtofishdetector.AsshowninFig.2,itisanactualstructuraldrawingwhenusedastransmittingandreceivingtransducer.Therubbersealstransducerandcableup.Thesoundwaveradiatessignaltowaterviaaperforatedrubberin1cmthickness.(Itonlyloses1dBwiththerubber,sotheinfluenceisnegligible.)Thetransducerbeyondtheradiatingsurfaceisusedfoamedrubbertosealup,whichmakessoundwaveradiatetoonedirection.郎之万型换能器在大功率振动状态下，易产生压电陶瓷片振裂现象；图3是复合棒形换能器的结构示意图。预应力螺杆使压电陶瓷片与前后盖板之间除了粘结外还紧紧地压紧，使其能承受更大的张压力，改善在大功率工作状态下陶瓷片损坏和脱胶现象。复合棒形换能器将前盖取为带锥度的轻金属，使换能器与水介质有更好的阻抗匹配，并增大辐射面积；后盖板采用带锥度的重金属，使尾部的声辐射变得很小，形成较好的自然单面辐射振子。Langevintransducereasilyaffectspiezoelectricceramic’svibrationcrackonceitisvibratingwithhighpower.Fig.3isthestructurediagramofcompoundbartransducer.Prestressedscrewcompressespiezoelectricceramicwithfrontandbackcovertightlybesidescementation;itcanbearstrongerpressure,whichimprovespiezoelectricceramic’sdamageanddegumminginhighpower.Thefrontcoverismadeoflightmetalwithtaper,whichbettermatchesthetransducerandaqueousmediuminimpedanceandincreasesradiatingarea.Thebackcoverismadeofheavymetalwithtaper,whichdecreasessoundradiationoftheempennageandformsawellnaturalsingle-sideradiationoscillator.