Electroacoustic transducer and method of fabricating the same

Abstract

The present invention provides an electroacoustic transducer and a method of fabricating the same, employing a lead frame to integrally form a plurality of component parts, thus reducing the number of individual component parts, and improving assembly efficiency. The electroacoustic transducer comprises a base, a yoke fixed to the base, a core, a coil wound around the core, magnet surrounding the coil, a support ring surround the magnet, a vibrating plate supported on the support ring, lead terminals fixed to the base, and a case having a sound emitting cylinder and joined to the base so as to cover those components. A gap is formed between the core and the diaphragm. The diaphragm, the gap, the core, the yoke and the magnet form a closed magnetic path. The coil drives the diaphragm for vibration when energized. The yoke and the lead terminals are integrally formed of a common metal material such as the lead frame. The core may be integrally formed with the yoke of the lead frame.

What is claimed is: 
     
       1. An electroacoustic transducer for converting . .electric signals.!. externally applied . .to lead terminals.!. .Iadd.electric signals .Iaddend.into sound, comprising: .Iadd.a case provided with .Iaddend.a base formed of a synthetic resin in the shape of a flat plate;   . .a case joined to the base and integrally provided with.!. a sound emitting cylinder .Iadd.formed on the case for emitting sound outside the case.Iaddend.;   a yoke . .formed of a metal and.!. fixed to an upper surface of the base and . .covered with.!. .Iadd.housed in .Iaddend.the case;   a core formed on an upper surface of the yoke;   a coil wound around the core;   an annular magnet disposed . .so as to surround.!. .Iadd.around .Iaddend.the coil;   . .a support ring disposed on the base so as to surround the magnet;.!.   a diaphragm .Iadd.formed .Iaddend.of .Iadd.a .Iaddend.magnetic material . .supported on the support ring.!. .Iadd.and disposed .Iaddend.so as to form a gap between the diaphragm and the core, said diaphragm forming a closed magnetic path.Iadd., .Iaddend.via the gap.Iadd., .Iaddend.with the core, yoke and magnet, and being vibrated by the excitation of the coil;   . .the.!. lead terminals formed of the same material as the yoke, fixed to the base, connected to ends of the coil and . .projecting.!. .Iadd.leading .Iaddend.outside the case; and   said yoke and said lead terminals formed of a common lead frame made of a single metal material.   
     
     
       2. An electroacoustic transducer according to claim 1, wherein the core is formed integrally with the yoke so as to protrude from the yoke. 
     
     
       3. An electroacoustic transducer according to claim 1, wherein the core is formed separately from the yoke and fixedly attached to the yoke. 
     
     
       4. An electroacoustic transducer according to claim 1, wherein .Iadd.the diaphragm is provided with .Iaddend.a magnetic piece . .is attached to the diaphragm.!. to increase the vibrating mass of the diaphragm. 
     
     
       5. A method of fabricating an electroacoustic transducer for converting .Iadd.externally applied .Iaddend.electric . .input.!. signals into sound, said method comprising: forming lead terminals and a yoke by a common lead frame made of a single metal material and forming a core . .integrally with.!. .Iadd.on .Iaddend.the yoke;   forming a base of synthetic resin on the lead frame by molding so that the . .yoke and the.!. lead terminals .Iadd.and the yoke .Iaddend.are fixed to the base;   winding a coil around the core formed . .integrally with.!. .Iadd.on .Iaddend.the yoke, and connecting ends of the coil to the lead terminals, said winding and connecting being carried out on the lead frame;   mounting a . .support ring on the yoke, fitting a.!. magnet . .in the support ring.!. .Iadd.on the yoke, .Iaddend.and placing a diaphragm . .on the support ring,.!. .Iadd.so as to form a gap between the diaphragm and the core, .Iaddend.said mounting. ., fitting.!. and placing being carried out on the lead frame;   placing a case on and fixedly joining the same to the base, said placing being carried out on the lead frame; and   cutting . .tie bars of.!. the lead . .frame extending from the yoke and the lead.!. terminals .Iadd.protruding from the case .Iaddend.to separate the electroacoustic transducer from the lead frame.   
     
     
       6. A method of fabricating an electroacoustic transducer. .,.!. according to claim 5, wherein the core is formed integrally with the yoke . .so as to protrude from the yoke.!. .Iadd.by the lead frame.Iaddend.. 
     
     
       7. A method of fabricating an electroacoustic transducer, according to claim 5, wherein the core is formed separately from the yoke and fixedly attached to the yoke in a forced fit. 
     
     
       8. A method of fabricating an electroacoustic transducer, according to claim 5, wherein the coil is formed by winding a wire around a bobbin mounted on the core. 
     
     
       9. A method of fabricating an electroacoustic transducer, according to claim 5, wherein the coil is formed by winding a wire around a bobbin, and then the bobbin holding the coil is mounted on the core.